Image production apparatus, image display apparatus, image display method and optical modulation device adjustment apparatus

ABSTRACT

An image production apparatus, an image display apparatus and an image display method are disclosed which can reduce the ununiformity in luminance and color which appears on a display screen and can be formed compact. Also optical modulation device adjustment apparatus is disclosed which can detect and correct the ununiformity in modulation characteristic of a modulation device. The image display apparatus includes a light detection apparatus in addition to a light source section, an illumination optical system, an optical modulation section, a spatial filter, a light projection section and a screen. The light detection apparatus detects the dispersion of a modulation characteristic of each pixel element of GLV devices and the ununiformity in luminance and color displayed in accordance with an illumination condition. An optimum driving voltage for minimizing the ununiformity in color and luminance to be displayed is determined based on a signal detected by the light detection apparatus.

This application is a continuation application of U.S. patentapplication Ser. No. 10/684,526 filed Oct. 15, 2003, the entire contentbeing incorporated by reference.

BACKGROUND OF THE INVENTION

The present invention relates to an image production apparatus, an imagedisplay apparatus, an image display method and an optical modulationdevice adjustment apparatus wherein a light diffraction modulationdevice such as, for example, a light valve device of the diffractiongrating type which diffracts or reflects light is used to produce ordisplay a two-dimensional image.

A method is known wherein, in order to assure a high resolution of animage on an image formation apparatus such as a projector or a printer,a light flux from a one-dimensional image display device is projectedonto an image formation element while being scanned by an opticalscanning means to form a two-dimensional image. The method is disclosed,for example, in U.S. Pat. No. 5,982,553 (hereinafter referred to patentdocument 1). As one of one-dimensional image display devices, a gratinglight valve (GLV) device developed by Silicon Light Machine of USA isknown and disclosed, for example, in Japanese Patent No. 3,164,824(hereinafter referred to as patent document 2) and U.S. Pat. No.5,841,579 (hereinafter referred to as patent document 3).

The GLV device is formed from a diffraction grating of the micromachinephase reflection type which makes use of diffraction of light. Where theGLV device is used, an image can be displayed by electricallycontrolling the gradation of the light.

Typically, in the GLV device, a pixel element which forms a pixel isformed from several ribbon electrodes of several μm in size, and severalhundreds to several thousands such pixel elements are disposed in aone-dimensional direction. The GLV device in the form of aone-dimensional image device which includes a plurality of pixelelements functions as a one-dimensional spatial modulator, andillumination light condensed in a one-dimensional direction is firstmodulated by the GLV device and then scanned in horizontal directions bymeans of a galvano mirror (polygon mirror) to form a two-dimensionalimage.

When compared with an ordinary two-dimensional display device, where theGLV device is used, also the number of pixels in a vertical direction ofa screen is equal to the number of pixels in the one-dimensionaldirection. However, since only a width at least equal to the width ofone pixel is required in the transverse direction, the number of pixelsnecessary for display of a two-dimensional image is small. The GLVdevice can be formed such that it has an active region of acomparatively small size and can achieve display of a high resolution, ahigh switching rate and a great band width. Meanwhile, since the GLVdevice can operate with a low application voltage, it is anticipatedthat a display device of a significantly reduced size can be realized.

When compared with an ordinary two-dimensional display device, forexample, a projector type display device using a liquid crystal panel,an image display apparatus which uses such a one-dimensional imagedisplay apparatus as described above, that is, a GLV device, canrepresent a very smooth and natural image since the GLV device itselfdoes not include a boundary between pixels. Further, if lasers of thethree primary colors of red, green and blue are used as light sourcesfor such GLV devices and lights from them are mixed, then an imagehaving a very wide and natural color reproduction range can berepresented. In this manner, an image display apparatus which uses theGLV device exhibits a superior displaying performance which cannot beachieved by the other conventional image display apparatus.

Actually, however, it is not easy to realize a good image display withfull pixels of an image display apparatus for 1,080×1,920 pixelsobtained by scanning a GLV device including, for example, 1,080 pixelelements. The reason is that usually it is difficult in production ofdevices to produce ribbon electrodes for formation of pixel elementsuniformly in terms of the shape and the surface state over an overalldisplay region. Therefore, also in a state wherein the pixel elementsare at rest, unevenness of approximately nm is exhibited between thepixel elements. Therefore, a GLV device as a modulator exhibitsdifferent modulation characteristics (driving voltage-modulated lightluminance) among different pixel elements. As a result, someununiformity in luminance appears on a screen, and there is a problemthat, for example, a uniform black image cannot be obtained.

Further, since driving circuits provided for the individual pixels foradjusting the gradation of luminance have some dispersion, it is noteasy to make the modulation characteristics of the pixel elementsuniform. For example, an error of a driving signal for moving a ribbonelectrode at the nm level disperses the amount of movement of a movableribbon electrode of the GLV device and gives rise to a variation inpixel element modulation characteristic.

Such dispersions in modulation characteristic are recognized astransverse stripes in a unit of one to several pixels on a displayscreen and causes deterioration of the picture quality.

Further, in order to illuminate a GLV device which is a one-dimensionalimage device, illumination light is condensed in a one-dimensionaldirection and is illuminated on a line on the GLV device. In thisinstance, it is not easy to make the illumination light intensityuniform over the overall illumination region. Even if uniformillumination can be realized by optical designing and initialadjustment, it is difficult to realize normally uniform illuminationlight due to an influence of a variation of a light source or an opticalsystem arising from a temperature variation or a secular change.Although such ununiformity in illumination is not comparativelyconspicuous where a single color is involved, where different colors areinvolved as in the case of a color image, the ununiformity inillumination is recognized as a color fault and deteriorates the picturequality. Particularly where different illumination systems are used fordifferent colors as in the case of a laser projector, such ununiformityin color is liable to appear.

Further, there is the possibility that the picture quality may bedeteriorated by processing of a driving signal to be applied to a pixelelement.

Usually, a digital driving signal inputted from a circuit in thepreceding stage is converted into an analog signal by a D/A (digital toanalog) conversion circuit and then inputted to a driving circuit,whereafter it is applied to a pixel element.

Where the D/A conversion circuit and the driving circuit have a smallerbit width than the preceding circuit, when a signal of the precedingstage having a greater bit width is inputted to the D/A conversioncircuit and the driving circuit, low order bits of the signal are cutand thinned out. Consequently, the signal exhibits comparativelydiscontinuous values, or in other words, the signal is quantized ordigitized.

The signal quantized in this manner exhibits rougher gradations and hasan error when compared with the driving signal in the preceding circuit.This is called quantization error.

The quantization error produces some discontinuity between pixels on ascreen. Since the eyes of the human being have a high sensitivity, suchsmall discontinuity between pixels is recognized as an unnatural displayto the human eyes. Particularly on a display apparatus wherein lightfrom a GLV device is scanned to form a two-dimensional image, throughscanning of a one-dimensional image on the screen, an abnormal point ofthe one-dimensional image makes a transverse stripe on the screen, whichis further likely to be sensed.

Further, an image display apparatus which employs a GLV devicenecessitates structural improvements such as an improvement inarrangement of a light source and optical parts in order to display acolor video image of a high quality while it is miniaturized.Particularly where different illumination systems are used for differentcolors as in the case of a laser projector, there is a technical problemof how to reduce the size of a display apparatus while it is realized tosynthesize the illumination lights of the different colors with a highdegree of quality and remove unnecessary illumination light componentsefficiently to reduce noise to the illumination lights to be used todisplay an image.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an image productionapparatus, an image display apparatus and an image display method whichcan reduce the ununiformity in luminance and color which appears on adisplay screen.

It is another object of the present invention to provide an opticalmodulation device adjustment apparatus which can detect and correct theununiformity in modulation characteristic of a modulation device.

It is a further object of the present invention to provide an imagedisplay apparatus which can be formed compact.

It is a still further object of the present invention to provide animage display apparatus which can suppress, while using a GLV device,the discontinuity of an image arising from a quantization error causedby a quantization process of a driving signal.

According to the first aspect of the present invention, there isprovided an image production apparatus, including:

an optical modulation device for modulating light;

a driving circuit for driving the optical modulation device in responseto an input signal;

an initial driving signal production circuit for producing an initialdriving signal for deriving the optical modulation device in response tothe input signal; and

correction means for determining, from a target light intensity ofmodulated light to be emitted from the optical modulation device inresponse to the initial driving signal and an intensity of the modulatedlight emitted from the optical modulation device in response to thedriving signal, a value of the driving signal for the optical modulationdevice corresponding to the target light intensity and inputting thedetermined driving signal to the driving circuit.

In the image production apparatus, the correction means which correctsan initial driving signal produced by the initial driving signalproduction circuit from an input signal is provided. The correctionmeans sets a target light intensity for modulated light to be emittedfrom the optical modulation device in response to the initial drivingsignal in advance, determines, from a result of measurement of the lightintensity of the modulated light in response to the diving signal, avalue of the driving signal for the optical modulation device with whichthe optical modulation device emits modulated light having the targetlight intensity, and inputs the determined driving signal to the drivingcircuit.

According to the second aspect of the present invention, there isprovided an image display apparatus, including:

a light source;

a plurality of optical modulation devices each including a plurality offixed electrodes and a plurality of displaceable electrodes positionedadjacent the fixed electrodes and individually displaced or deformed inresponse to a driving signal applied thereto to form offsets from thefixed electrodes so that illumination light from the light sourceincoming to one of faces of the fixed and displaceable electrodes ismodulated in accordance with the offsets such that the modulated lightsfrom the optical modulation devices are arrayed linearly to form aone-dimensional image;

image display means for being illuminated with the modulated lights toform an image;

a driving circuit for applying the driving signals to the electrodes ofthe optical modulation devices in response to an input signal thereto;

an initial driving signal production circuit for producing an initialdriving signal for driving the optical modulation devices from the inputsignal; and

correction means interposed between the initial driving signalproduction circuit and the driving circuit for determining, from atarget light intensity for the modulated lights to be emitted from theoptical modulation devices in response to the initial driving signal andintensities of the modulated lights emitted from the optical modulationdevices in response to the driving signals, values of the drivingsignals for the optical modulation devices corresponding to the targetlight intensity and inputting the driving signals of the determinedvalues to the driving circuit.

In the image display apparatus, the correction means which corrects aninitial driving signal produced by the initial driving signal productioncircuit from an input signal is provided. The correction means sets atarget light intensity for modulated light to be emitted from theoptical modulation device in response to the initial driving signal inadvance, determines, from a result of measurement of the light intensityof the modulated light in response to the diving signal, a value of thedriving signal for the optical modulation device with which the opticalmodulation device emits modulated light having the target lightintensity, and inputs the determined driving signal to the drivingcircuit.

According to the third aspect of the present invention, there isprovided an image display method for scanning modulated lights emittedfrom a plurality of optical modulation devices, each of which includes aplurality of fixed electrodes and a plurality of displaceable electrodespositioned adjacent the fixed electrodes and individually displaced ordeformed in response to a driving signal applied thereto to form offsetsfrom the fixed electrodes so that illumination light from a light sourceincoming to one of faces of the fixed and displaceable electrodes ismodulated in accordance with the offsets such that the modulated lightsfrom the optical modulation devices are arrayed linearly to form aone-dimensional image, on a plane to display a two-dimensional image,including:

a driving signal correction step of determining, before an image isdisplayed, from a target light intensity of the modulated lights emittedfrom the optical modulation devices in response to an initial drivingsignal produced from an input signal and intensities of the modulatedlights emitted from the optical modulation devices in response to thedriving signals, values of the driving signals for the opticalmodulation devices corresponding to the target light intensity; and

a step of applying, when an image is to be displayed, the drivingsignals of the determined values to the optical modulation devices todrive the optical modulation elements.

In the image production method, before an image is displayed, a targetlight intensity is set in advance for the modulated light to be emittedfrom the optical modulation devices in response to an initial drivingsignal, and a value of the driving signal with which modulated lighthaving the target light intensity of the optical modulation devices isemitted is determined from a result of measurement of the lightintensity of the modulated light emitted in accordance with the drivingsignal. Then, when an image is to be displayed, the determined drivingsignal is applied to each of the optical modulation device to drive theoptical modulation device. Consequently, an image of a high quality freefrom ununiformity in luminance and color can be displayed.

According to the fourth aspect of the present invention, there isprovided an optical modulation device adjustment apparatus, including:

a light source;

a plurality of optical modulation devices each including a plurality offixed electrodes and a plurality of displaceable electrodes positionedadjacent the fixed electrodes and individually displaced or deformed inresponse to a driving signal applied thereto to form offsets from thefixed electrodes so that illumination light from the light sourceincoming to one of faces of the fixed and displaceable electrodes ismodulated in accordance with the offsets such that the modulated lightsfrom the optical modulation devices are arrayed linearly to form aone-dimensional image;

a driving circuit for applying the driving signals to the electrodes ofthe optical modulation devices in response to an input signal thereto;

an initial driving signal production circuit for producing an initialdriving signal for driving the optical modulation devices from the inputsignal;

measurement means removably placed at a position at which themeasurement means can measure the modulated lights emitted from theoptical modulation devices for measuring the intensities of themodulated lights emitted from the optical modulation devices anddetermining a modulation characteristic of each of the opticalmodulation devices representative of a relationship between the drivingsignal applied to the optical modulation device and the intensity of themodulated light emitted from the optical modulation device; and

correction means interposed between the initial driving signalproduction circuit and the driving circuit for determining, from themeasured modulation characteristics of the optical modulation devicesand a target light intensity for the modulated lights to be emitted fromthe optical modulation devices in response to the initial drivingsignal, values of the driving signals for the optical modulation devicescorresponding to the target light intensity and inputting the drivingsignals of the determined values to the driving circuit.

In the optical modulation device adjustment apparatus, the measurementmeans and the correction means are provided. The measurement meansmeasures modulated lights from the modulation devices to determine themodulation characteristics (driving voltage-modulated light intensity(or luminance)) of the modulation elements. The correction means sets atarget light intensity in advance for the modulated lights to be emittedfrom the optical modulation devices in response to an initial drivingsignal. Then, the correction means determines, from the measuredmodulation characteristics of the optical modulation devices, values ofthe driving signals for the optical modulation devices with which theyemit modulated lights having the target light intensity.

According to the fifth aspect of the present invention, there isprovided an image display apparatus for successively displaying aplurality of frames in which a plurality of pixels are disposed in amatrix, including:

a plurality of pixel elements for individually forming the pixels;

a driving circuit for applying a driving signal to the pixel elements;and

driving signal supply means for allocating, when a predetermined objectone of the pixels is to be displayed, a quantization error appearing,when driving signal data is inputted to the driving circuit, in thedriving signal of an object pixel element which corresponds to theobject pixel to plural ones of the pixels in the proximity of the objectpixel in a current frame being displayed and plural ones of the pixelswithin a predetermined range in a frame displayed next to the currentframe, adding the allocated quantization error components to the drivingsignal data for the plural ones of the pixel elements and inputting theresulting driving signal data to the driving circuit.

According to the sixth aspect of the present invention, there isprovided driving signal supply means including:

data division means for dividing driving signal data having a bit widthof m into a high order bit part having a bit number of n smaller than mand a low order bit part having another bit number of m−n;

first addition means for adding the low order bit part and a precedingerror allocated in the immediately preceding error allocation processand outputting a sum total of the errors;

error rounding process means having a predetermined threshold value forcomparing the sum total of the errors outputted from the first additionmeans with the threshold value and outputting first data or second datafrom a result of the comparison;

second addition means for adding the high order bit part and the firstdata or the second data outputted from the error rounding process meansto produce driving signal data having a bit width of n and inputting thedriving signal data to the driving circuit;

subtraction means for subtracting the first data or the second dataoutputted from the error rounding process means from the sum total ofthe errors outputted from the first addition means and outputting thedifference as a current error; and

error allocation means for multiplying the current error outputted fromthe subtraction means by predetermined weighting coefficients,allocating the weighted errors to the plural ones of the pixels in theproximity of the object pixel in the current frame and the plural onesof the pixels within the predetermined range in the frame displayed nextto the current frame and inputting the allocated current error to thefirst addition means.

In the image display apparatus, a quantization error which appears whendriving signal data having a comparatively great bit width, that is,having a high degree of accuracy, is inputted to the driving circuitwhich has a comparatively small bit width is subject to athree-dimensional error diffusion (intraframe and interframe) process bythe driving signal supply means to reduce the discontinuity of imagedisplays. In this manner, an image of a picture quality equivalent tothat of a comparatively high bit driving circuit is displayed using acomparatively low bit driving circuit.

According to the seventh aspect of the present invention, there isprovided an image display apparatus for successively displaying aplurality of frames each including a two-dimensional image, including:

a light source;

a plurality of optical modulation devices each including a plurality offixed electrodes and a plurality of displaceable electrodes positionedadjacent the fixed electrodes and individually displaced or deformed inresponse to a driving signal applied thereto to form offsets from thefixed electrodes so that illumination light from the light sourceincoming to one of faces of the fixed and displaceable electrodes ismodulated in accordance with the offsets such that the modulated lightsfrom the optical modulation devices are arrayed linearly to form aone-dimensional image formed from a string of pixels;

a driving circuit for applying the driving signals to the electrodes ofthe optical modulation devices;

image display means for being illuminated with the modulated lights toform the two-dimensional image in which strings of the pixels aredeveloped;

first driving signal supply means for outputting driving signal data forthe optical modulation devices; and

second driving signal supply means for allocating, when a predeterminedobject one of the pixels is to be displayed, a quantization errorappearing, when the driving signal data is inputted to the drivingcircuit, in the driving signal for the optical modulation devices toplural ones of the pixels in the proximity of the object pixel in acurrent frame being displayed and plural ones of the pixels within apredetermined range in a frame displayed next to the current frame,adding the allocated quantization error components to the driving signaldata for the plural ones of the pixel elements and inputting theresulting driving signal data to the driving circuit.

In the image display apparatus, a quantization error which appears whendriving signal data having a comparatively great bit width, that is,having a high degree of accuracy, is inputted to the driving circuitwhich has a comparatively small bit width is subject to athree-dimensional error diffusion (intraframe and interframe) process bythe driving signal supply means to reduce the discontinuity of imagedisplays. In this manner, an image of a picture quality equivalent tothat of a comparatively high bit driving circuit is displayed using acomparatively low bit driving circuit.

With the image production apparatus, image display apparatus, imagedisplay method and optical modulation device adjustment apparatusaccording to the present invention, the optical modulation elements aredriven with corrected driving signals which are corrected in terms ofthe ununiformity in illumination condition and the dispersion in pixelelement characteristic for each pixel. Consequently, a video image of ahigh quality free from ununiformity in luminance and color can beprovided on the screen.

Further, since only the ununiformity in illumination condition which isliable to be influenced by an environmental variation and a secularchange is detected and corrected, a stable video image of a high picturequality free from ununiformity in color can be provided. Further, sinceonly an illumination condition is measured, the measurement time can bereduced significantly, which is advantageous in practical use.Furthermore, a maximum luminance function is set for each of divisionalillumination regions, the luminance of illumination light can beutilized effectively without being wasted.

Further, since a quantization error which appears upon production of acorrection table is diffused uniformly into and added to imageinformation, a correction error or a defect in picture quality which mayappear secondarily can be reduced. Through the process described, evenwhere a driving circuit of a comparatively small bit width is used,correction of unevenness in display in the form of a strike equivalentto that of a driving circuit of a comparatively great bit width can beachieved. Consequently, reduction in cost of the driving circuits can beanticipated.

Furthermore, since the ununiformity correction function is incorporated,moderation of the tolerance in design of the illumination optical systemand reduction of man-hours for adjustment of the optical system can beanticipated. Consequently, the cost of the entire system can be reduced.

The above and other objects, features and advantages of the presentinvention will become apparent from the following description and theappended claims, taken in conjunction with the accompanying drawings inwhich like parts or elements denoted by like reference symbols.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a configuration of an image displayapparatus according to a first embodiment of the present invention;

FIG. 2 is a schematic view showing an arrangement of components of theimage display apparatus according to the first embodiment;

FIGS. 3 to 5 are schematic views illustrating operation of a lightdiffraction modulation device used in the image display apparatusaccording to the first embodiment;

FIGS. 6A to 6C are diagrams illustrating a characteristic of lightbefore it is introduced into an illumination optical system of the imagedisplay apparatus according to the first embodiment;

FIGS. 7A to 7C are diagrammatic views illustrating a function of theillumination optical system of the image display apparatus according tothe first embodiment;

FIGS. 8A to 8C are diagrammatic views illustrating a principle of aspatial filter section of the image display apparatus according to thefirst embodiment;

FIGS. 9A and 9B are diagrammatic views illustrating a function of alight diffusion section of the image display apparatus according to thefirst embodiment;

FIGS. 10A to 10D are diagrammatic views illustrating appearance of ahorizontal stripe on a screen due to the dispersion in characteristic ofan optical modulation device in a second embodiment of the presentinvention;

FIG. 11 is a diagram illustrating the ununiformity in luminance andcolor appearing on a screen due to the ununiformity of a light sourceillumination condition in the second embodiment of the presentinvention;

FIG. 12 is a block diagram showing a configuration of an image displayapparatus according to the second embodiment;

FIG. 13 is a schematic view showing arrangement of components of theimage display apparatus according to the second embodiment;

FIG. 14 is a flow chart illustrating a process of detecting andcorrecting the ununiformity in display by the image display apparatusaccording to the second embodiment;

FIG. 15 is a block diagram showing a configuration of a signalprocessing system of the image display apparatus according to the secondembodiment;

FIG. 16 is a flow chart illustrating a process of detecting theununiformity in display by the image display apparatus according to thesecond embodiment;

FIGS. 17A and 17B are diagrams illustrating a test signal to be appliedto an optical modulation device in order to detect the ununiformity indisplay and an output signal of a photo-detector of the image displayapparatus according to the second embodiment;

FIG. 18 is a diagram illustrating an example of the sensitivity of thelight detector of the image display apparatus according to the secondembodiment;

FIG. 19 is a diagram illustrating a position distribution of lightsemitted from the optical modulation devices of the image displayapparatus according to the second embodiment;

FIG. 20 is a block diagram showing a configuration of a correctionarithmetic operation section of the image display apparatus according tothe second embodiment;

FIG. 21 is a flow chart illustrating a process of correcting theununiformity in display by the image display apparatus according to thesecond embodiment;

FIG. 22 is a diagram illustrating a profile of a white luminance whichcan be realized by the image display apparatus according to the secondembodiment;

FIG. 23 is a diagram illustrating a target modulation characteristicobtained from the profile of the white luminance illustrated in FIG. 22;

FIGS. 24A and 24B are diagrams illustrating a method of correcting adriving voltage with a measured modulation characteristic of amodulation device and the target modulation characteristic of the imagedisplay apparatus according to the second embodiment;

FIG. 25 is a diagram illustrating a result of the correction by themethod illustrated in FIGS. 24A and 24B;

FIG. 26 is a diagram illustrating a profile of a white luminance afterthe ununiformity in display is corrected by the image display apparatusaccording to the second embodiment;

FIG. 27 is a flow chart illustrating a process of detecting andcorrecting the ununiformity in display by an image display apparatusaccording to a third embodiment of the present invention;

FIG. 28 is a schematic diagrammatic view showing a configuration of ameasuring instrument for measuring a modulation characteristic of amodulation device in advance in the image display apparatus according tothe third embodiment;

FIG. 29 is a flow chart illustrating a process of detecting a modulationcharacteristic of the modulation device in advance in the image displayapparatus according to the third embodiment;

FIGS. 30A and 30B are diagrams illustrating a test signal and amodulation characteristic of a modulation device measured in advance inthe image display apparatus according to the third embodiment,respectively;

FIG. 31 is a diagram illustrating a position distribution of themodulation characteristics of the modulation devices measured in advancein the image display apparatus according to the third embodiment;

FIGS. 32A and 32B are diagrams illustrating a test signal to be appliedto an optical modulation device in order to detect an illuminationprofile in the image display apparatus according to the third embodimentand an output signal of a light sensor, respectively;

FIG. 33 is a flow chart illustrating a process of detecting only anillumination profile by the image display apparatus according to thethird embodiment;

FIG. 34 is a block diagram showing a configuration of a correctionarithmetic operation section of the image display apparatus according tothe third embodiment;

FIG. 35 is a flow chart illustrating a process of correcting a detectedununiformity in display by the image display apparatus according to thethird embodiment;

FIG. 36 is a diagram illustrating illumination profiles which do notinclude any characteristic of the modulation devices measuredimmediately prior to display by the image display apparatus according tothe third embodiment;

FIG. 37 is a diagram illustrating a profile of a white luminance whichcan be realized by the image display apparatus according to the thirdembodiment;

FIG. 38 is a diagram illustrating a method of dividing a profile of awhite luminance into a plurality of regions and determining targetmodulation characteristics in the divisional regions by the imagedisplay apparatus according to the third embodiment;

FIG. 39 is a diagram illustrating a profile of a white luminance afterthe ununiformity in display is corrected by the image display apparatusaccording to the third embodiment;

FIG. 40 is a block diagram showing a partial configuration of a signalprocessing section of an image display apparatus according to a fourthembodiment of the present invention;

FIG. 41 is a block diagram showing a configuration of an error diffusioncircuit of the image display apparatus according to the fourthembodiment;

FIG. 42 is a diagrammatic view showing an example of two-dimensionalerror diffusion of the image display apparatus according to the fourthembodiment;

FIG. 43 is a diagrammatic view showing a structure of an image by theimage display apparatus according to the fourth embodiment;

FIG. 44 is a diagrammatic view showing an example of three-dimensionalerror diffusion of the image display apparatus according to the fourthembodiment; and

FIG. 45 is a block diagram showing a configuration of an imageproduction apparatus according to a fifth embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED. EMBODIMENTS

First Embodiment

Referring first to FIG. 1, there is shown an example of a configurationof an image display apparatus according to a first embodiment of thepresent invention. The image display apparatus shown is generallydenoted by 1 and formed as a projector which employs a plurality ofmodulation devices in the form of GLV (Grating Light Valve).

The image display apparatus 1 includes an optical system 1 a, a signalprocessing section 9, and a power supply 90.

The optical system 1 a includes a light source section 2, anillumination optical system 3, an optical modulation section 4, aspatial filter (SFT) 5, a light projection section 6, and a screen 8.

The signal processing section 9 includes a video signal input processingsection (VSIP) 27, an element driving circuit section (DRV) 28, a systemcontrol section (CPU) 29, and a scan control section (SCMCNT) 30.

The video signal input processing section (VSIP) 27 serves as an initialdriving signal production circuit.

The element driving circuit section (DRV) 28 serves as a drivingcircuit.

In the following, functions of the components mentioned above are firstdescribed simply, and then a configuration and operation of each of thecomponents are described in detail with reference to FIG. 2 which showsarrangement of the components in the image display apparatus 1.

The light source section 2 includes, for example, laser diodes for red(R), green (G) and blue (B). In particular, the light source section 2includes a red laser (LD(R)) 21R, a green laser (LD(G)) 21G and a bluelaser (LD(B)) 21B for emitting red, green and blue laser beams,respectively. The laser diodes 21R, 21G and 21B receive supply of powerfrom the power supply (PWR) 90 and emit laser beams of the respectivecolors.

The illumination optical system 3 includes a red illumination opticalsystem (LG(R)) 22R, a green illumination optical system (LG(G)) 22G anda blue illumination optical system (LG(B)) 22B. The illumination opticalsystem 3 further includes shape changing means for changing the shape ofthe cross sections of the laser beams emitted from the red laser 21R,green laser 21G and blue laser 21B in accordance with the shape of GLVdevices arranged one-dimensionally, a converging lens for convergingeach of the laser beams from the shape changing means and a directionchanging mirror for condensing the converged laser beams on an opticalmodulation device.

The optical modulation section 4 includes a red GLV device (GLV(R)) 23R,a green GLV device (GLV(G)) 23G and a blue GLV device (GLV(B)) 23B, anda color synthesis section (MX) 24. Each of the GLV devices 23R, 23G and23B includes an array of pixels arranged one-dimensionally and is usedto display a one-dimensional image.

More particularly, each of the GLV devices 23R, 23G and 23B includes,for example, 1,080 pixel elements arranged one-dimensionally fordisplaying 1,080 pixels and operates when a driving voltagecorresponding to an image signal is applied thereto to reflect ordiffract illumination light emitted from the illumination optical system3, introduced into the GLV device and converging in a one-dimensionaldirection to emit reflected light or diffracted light including a 0thorder light, ±first order lights and ±second order lights. In otherwords, each of the GLV devices 23R, 23G and 23B functions as amodulation means for modulating a laser beam in accordance with an imagesignal.

The color synthesis section (MX) 24 includes color synthesis filters forsynthesizing or multiplexing red, green and blue modulated lightsmodulated by the GLV devices 23R, 23G and 23B, respectively, to producemodulated lights of various colors to display a color image. Here, thecolor synthesis section 24 serves as a color synthesis means.

The spatial filter (SFT) 5 includes, for example, a concave mirror and aconvex mirror to select, from among the modulated lights produced by theGLV devices 23R, 23G and 23B, the ±first order diffracted lights whichhave the highest intensity and are to be used to display an image so asto pass through the optical system while intercepting the othercomponents which are not to be used for image display. Here, the spatialfilter serves as a display separation means.

The light projection section 6 includes a light diffusion section(diffuser) (DIFF) 7, a projection lens (PJL) 25 and a scanning mirror(SCM) 26.

The light diffusion section 7 diffuses the ±first order diffractedlights so as to increase the cross section of them in a one-dimensionaldirection to convert them into linear diffused light. The projectionlens 25 projects the resulting first order diffused light onto thescanning mirror 26. The scanning mirror 26 is formed from, for example,a galvano mirror and rotates in synchronism with a video signal toproject the first order diffused light onto the screen 8 and scan thefirst order diffused light in a predetermined direction to form aprojected display image on the screen 8.

In the signal processing section 9, the video signal input processingsection 27 converts a video image signal VIDEO inputted, for example,from a video reproduction apparatus for a DVD (Digital Versatile Disk)from color difference signals YCbCr (YPbPr) into RGB signals. Since thevideo image signal VIDEO has a non-linear characteristic (γcharacteristic) applied thereto, the video signal input processingsection 27 performs an inverse gamma correction process for the RGBsignals to convert the non-linear characteristic of them into a linearcharacteristic. Then, in order for the RGB signals to correspond to thecolor reproduction range of the illumination light sources, the videosignal input processing section 27 performs a color space conversionprocess for the RGB signals. Then, the video signal input processingsection 27 inputs the resulting video signals to the element drivingcircuit section 28.

The element driving circuit section 28 receives the signals outputtedfrom the video signal input processing section 27 and applies them tothe GLV devices 23R, 23G and 23B at a predetermined timing to drive theGLV devices 23R, 23G and 23B so that the laser lights emitted from thered laser 21R, green laser 21G and blue laser 21B may be modulated,respectively.

The scan control section 30 outputs a signal for driving and controllingrotation of the scanning mirror 26 to the scanning mirror 26.

The system control section (CPU) 29 controls the video signal inputprocessing section (VSIP) 27, element driving circuit section (DRV) 28and scan control section (SCMCNT) 30 to establish synchronism among thedriving voltage signals to be applied from the element driving circuitsection 28 to the GLV devices 23R, 23G and 23B, the output signal of thescan control section (SCMCNT) 30, the operation timings of the GLVdevices 23R, 23G and 23B, and the rotation timing of the scanning mirror26.

Accordingly, the image display apparatus 1 operates in the followingmanner to display a two-dimensional color image.

Lights of the three primary colors emitted from the light sources 21R,21G and 21B are individually condensed in a one-dimensional direction bythe illumination optical system 3 and illuminated on the GLV devices23R, 23G and 23B for the colors, respectively. Each of the pixelelements of the GLV devices 23R, 23G and 23B controls the diffractionstate of the corresponding incoming light in accordance with the drivingsignal applied thereto from the element driving circuit section 28 tomodulate the illumination light of the corresponding color.

The modulated lights of R, G and B are condensed by the color synthesissection 24 to synthesize a modulated light of a desired color.

Thereafter, unnecessary modulated lights other than the ±first orderdiffracted lights are removed from the modulated light by the spatialfilter 5, and the resulting modulated light is converted into diffusedlight by the light diffusion section (DIFF) 7. The resulting first ordermodulated diffused light is introduced into the scanning mirror 26 pastthe projection lens 25. Based on the rotation driving signal inputtedfrom the scan control section (SCMCNT) 30, the scanning mirror 26 scansthe first order modulated diffused light on the screen 8 in synchronismwith the video image signal VIDEO and the driving signals applied to theGLV devices 23R, 23G and 23B from the element driving circuit section 28to form a two-dimensional color image on the screen 8.

FIG. 2 shows an example of arrangement of the components described aboveof the image display apparatus 1.

Referring to FIG. 2, in the image display apparatus 1 shown, the greenlaser 21G and the blue laser 21B are arranged such that they emit laserlights in directions parallel to the plane of FIG. 2 while the red laser21R is arranged such that it emits a red laser beam perpendicularly tothe plane of FIG. 2.

Now, a configuration and a principle of operation of the GLV devices23R, 23G and 23B which are major components of the image displayapparatus 1 are described with reference to the FIGS. 3 to 5. In thefollowing description, for the convenience of description, where thereis no necessity to distinguish the GLV devices 23R, 23G and 23B from oneanother, any of them is represented as a GLV device 23.

FIG. 3 is a partial schematic perspective view of a GLV device 23 fordisplaying a one-dimensional image.

Referring to FIG. 3, the GLV device 23 shown includes a common electrode12 formed from a polycrystalline silicon thin film on a siliconsubstrate not shown, and strip-like ribbon electrodes 10 a, 11 a, 10 b,11 b, 10 c, 11 c and 10 d formed in a spaced relationship by apredetermined distance above the common electrode 12. Each of the ribbonelectrodes 10 a, 11 a, 10 b, 11 b, 10 c, 11 c and 10 d has a reflectionfilm (not shown) formed on an upper face thereof and thereby acts as areflection member.

As shown in FIG. 3, if a driving voltage is applied to the ribbonelectrodes 10 a, 10 b, 10 c and 10 d, then electrostatic force isgenerated between the ribbon electrodes 10 a, 10 b, 10 c and 10 d andthe common electrode 12. Consequently, the electrostatic force moves ordeforms the ribbon electrodes 10 a, 10 b, 10 c and 10 d in an upward ordownward direction in FIG. 3 in accordance with the driving voltagethereto thereby to change the height of the reflection films of theribbon electrodes 10 a, 10 b, 10 c and 10 d. Meanwhile, the ribbonelectrodes 11 a, 11 b and 11 c remain at fixed positions and do notmove.

The ribbon electrodes 10 a, 10 b, 10 c and 10 d which can be moved ordeformed may be hereinafter referred to as movable ribbon electrodes,and the ribbon electrodes 11 a, 11 b and 11 c which do not move may behereinafter referred to as fixed ribbon electrodes.

The ribbon electrodes may have, for example, the followingrepresentative dimensions. In particular, the width of the electrodes is3 to 4 μm; the gap between adjacent electrodes is approximately 0.6 μm;and the length of the electrodes is 200 to 400 μm.

A plurality of ribbon electrodes can be used in a set for one pixel. Forexample, the six adjacent ribbon electrodes 10 a, 11 a, 10 b, 11 b, 10 cand 11 c shown in FIG. 3 can be used so as represent one pixel. In thisinstance, the width of one pixel is approximately 25 μm.

For example, a GLV device which displays 1,080 pixels and is beingplaced into practical use includes a large number of ribbon electrodesfor 1,080 pixels along a transverse direction of FIG. 3.

A principle of operation of the GLV device 23 is described withreference to FIGS. 4 and 5.

FIGS. 4 and 5 are sectional views of the GLV device 23 in a transversedirection shown in FIG. 3. Referring to FIG. 4, the driving voltage tothe movable ribbon electrodes 10 a, 10 b, 10 c and 10 d is OFF, and thefixed ribbon electrodes 11 a, 11 b and 11 c are grounded. This state isreferred to as an OFF state of the GLV device 23.

Since the image display apparatus 1 is configured such that only the±first order diffracted lights are condensed on the screen 8, when theGLV device 23 is in the OFF state as describe above, the screen 8display black.

If illumination light is illuminated on the ribbon electrodes in thisstate, then no difference appears among all of the light paths of thereflected lights reflected by the ribbon electrodes 10 a, 11 a, 10 b, 11b, 10 c, 11 c and 10 d, but only diffracted lights of even-numberedorders such as 0th order lights (in an ordinary reflection direction)and ±second order lights are produced.

Since the image display apparatus 1 is configured such that only the±first order diffracted lights are condensed on the screen 8, when theGLV device 23 is in the OFF state as described above, the screen 8displays the black.

Referring now to FIG. 5, a predetermined driving voltage is applied tothe movable ribbon electrodes 10 a, 10 b, 10 c and 10 d while the fixedribbon electrodes 11 a, 11 b and 11 c are grounded.

As seen in FIG. 5, the movable ribbon electrodes 10 a, 10 b, 10 c and 10d to which the driving voltage is applied are displaced downward towardthe common electrode 12 side by the electrostatic force.

For example, where the wavelength λ of the incoming light is 532 nm, ifthe movable ribbon electrodes 10 a, 10 b, 10 c and 10 d are displaced byλ/4 in response to the driving voltage applied thereto, then they moveby λ/4=133 nm. When the amount of movement of the movable ribbonelectrodes 10 a, 10 b, 10 c and 10 d is λ/4, the diffraction efficiencyof first order light exhibits its maximum.

In this state, if illumination light is introduced to the ribbonelectrodes, then the total light path difference between light fluxesreflected by the movable ribbon electrodes 10 a, 10 b, 10 c and 10 d andlight fluxes reflected by the fixed ribbon electrodes 11 a, 11 b and 11c is equal to the half wavelength λ/2. Consequently, the GLV device 23functions as a reflection type diffraction grating and producesdiffracted lights including ±first order lights and ±third order lightsbecause the reflected light fluxes (0th order lights) interfere with andcancel each other.

The diffracted lights of the different order, numbers produced by theGLV devices 23R, 23G and 23B advance in directions determined by thespatial periods of the GLV devices 23R, 23G and 23B, that is, aremodulated spatially. The diffracted lights are synthesized by the colorsynthesis section 24, which includes first color synthesis filter 24 aand second color synthesis filter 24 b, to form a light flux of adesired color. Then, the spatial filter 5, which includes an Offnerrelay mirror 5 a and a Schlieren filter 5 b, removes the diffractedlights other than the ±first order lights from the light flux of thedesired color. The remaining ±first order lights are diffused by thelight diffusion section (diffuser) 7 and projected onto the scanningmirror 26 through the projection lens 25. The scanning mirror 26deflects the diffracted lights onto the screen 8 to form aone-dimensional image. Further, since the scanning mirror 26 is rotatingin response to an image signal, it scans the diffracted lights and theone-dimensional image on the screen 8 to form a color image.

Now, the other components of the image display apparatus 1 shown in FIG.2 are described.

As described hereinabove, the illumination optical system 3 includes thered illumination optical system 22R, green illumination optical system22G and blue illumination optical system 22B. The illumination opticalsystem 3 changes the cross sectional shape of the light beams from thered laser 21R, green laser 21G and blue laser 21B in accordance with theshape of the GLV devices 23R, 23G and 23B each in the form of aone-dimensional image element and illuminates the light beams of thechanged cross sectional shapes upon the GLV devices 23R, 23G and 23B,respectively.

As seen in FIG. 2, the red illumination optical system 22R includes aline generator expander 45. The green illumination optical system 22Gincludes a line generator expander 46, a mirror 48 and a converging lens49. The blue illumination optical system 22B includes a line generatorexpander 41, a converging lens 43 and a mirror 44.

Each of the line generator expanders 45, 46 and 41 includes two opticallenses and forms a linear laser light for being illuminated on acorresponding one of the GLV devices 23R, 23G and 23B arranged linearly.

FIG. 6A and FIGS. 6B and 6C illustrate the cross sectional shape and thespatial intensity distribution of a laser beam immediately before it isintroduced into one of the illumination optical systems 22R, 22G and 22Bafter it is emitted from a corresponding one of the laser light sources21R, 21G and 21B. Referring to FIGS. 6A, 6B and 6C, the x axis indicatesa direction parallel to the ribbon electrodes of each GLV device andhence is a direction perpendicular to the plane of FIG. 5. The y axisindicates the longitudinal direction of each GLV device and henceextends along the array direction of the ribbon electrodes andperpendicularly to the ribbon electrodes. In FIGS. 6B and 6C, the axis Iindicates the light intensity.

The laser beam emitted from each of the laser light sources 21R, 21G and21B has a spot-like cross section as indicated by a solid line in FIG.6A. In FIG. 6A, the position of any of the GLV devices 23R, 23G and 23Bis indicated by a broken line for comparison with the shape of the beam.

FIG. 6B indicates the illumination light intensity distribution of anyof the GLV devices 23R, 23G and 23B in a direction perpendicular to theribbon electrodes. Meanwhile, FIG. 6C indicates the illumination lightintensity distribution of any of the GLV devices 23R, 23G and 23B in itslongitudinal direction.

As seen from FIGS. 6A to 6C, the laser beam emitted from each of thelaser light sources 21R, 21G and 21B but not shaped by the illuminationoptical system 3 can illuminate only part of a corresponding one of theGLV devices 23R, 23G and 23B, and the intensity distribution of theillumination light is not uniform.

FIG. 7A and FIGS. 7B and 7C illustrate the cross sectional shape and thespatial intensity distribution of a laser beam emitted after it isemitted from one of the laser light sources 21R, 21G and 21B and thenshaped by a corresponding one of the illumination optical systems 22R,22G and 22B. Referring to FIGS. 7A, 7B and 7C, the x axis, the y axisand the I axis are defined similarly as in the case of FIGS. 6A, 6B and6C.

As seen from FIGS. 7A to 7C, the laser beams from the laser lightsources 21R, 21G and 21B are shaped by and emitted from the illuminationoptical systems 22R, 22G and 22B, respectively. More particularly, eachof the laser beams is shaped such that it is converged to a widthsubstantially equal to the width of the ribbon electrodes in thedirection of the ribbon electrodes and illuminates all of the ribbonelectrodes in the array direction of the ribbon electrodes of the GLVdevice. Accordingly, each of the laser beams emitted from theillumination optical systems 22R, 22G and 22B has a linear crosssectional shape extending in the direction of the array of the ribbonelectrodes of the GLV device and thus illuminates the overall area ofthe GLV device.

Since the ribbon electrodes of the GLV device have a small size, thelight fluxes emitted from the illumination optical systems 22R, 22G and22B must have a sufficiently small size in the direction of the x axis.

Referring back to FIG. 2, the linear blue laser beam emitted from theline generator expander 41 is converged by the converging lens 43,deflected by the mirror 44 and condensed on the GLV device 23B. Thelinear green laser beam emitted from the line generator expander 46 isdeflected by the mirror 48, converged by the converging lens 49 andcondensed on the GLV device 23G. The linear red laser beam emitted fromthe line generator expander 45 is converged and deflected by theconverging lens and the mirror not shown and condensed on the GLV device23R. Here, the line generator expanders 41, 45 and 46 serve as firstshaping means and the converging lenses 43 and 49 serve as firstconverging lenses while the mirrors 44 and 48 serve as first deflectingmirrors.

In each of the GLV devices 23R, 23G and 23B each having a function of aspatial modulator, each of the ribbon electrodes of each pixel elementis displaced in response to a driving voltage applied thereto tomodulate incoming laser light and emit modulated light includingdiffracted lights of even-numbered orders such as a 0th order light and±second order lights or diffracted lights of odd-numbered orders such as±first order lights and ±third order lights. The diffracted lights ofthe individual numbered orders advance in directions determined by thespatial periods of the GLV devices 23R, 23G and 23B, that is, arespatially modulated by the GLV devices 23R, 23G and 23B.

The modulated lights of the different colors thus emitted are mixed bythe color synthesis section 24 to form laser light of a desired color.

The color synthesis section 24 includes a first color synthesis filter24 a and a second color synthesis filter 24 b.

The red laser light modulated by the GLV device 23R and the green laserlight modulated by the GLV device 23G are first synthesized by the firstcolor synthesis filter 24 a.

Then, the blue laser light modulated by the GLV device 23B issynthesized with the laser light synthesized by the first colorsynthesis filter 24 a by the second color synthesis filter 24 b.

Consequently, the modulated lights of the three colors modulated by thethree GLV devices are color-synthesized.

Since the luminance of the blue laser light is lower than those of thegreen and red laser lights, if the blue light is synthesized as it iswith the green light or the red light, then the blue light component isweakened by the green or red light component due to the difference inluminance. Since the luminances of the red laser and the green laser areproximate to each other, the red and green lights can becolor-synthesized without the necessity to perform adjustment of theluminance levels.

The spatial filter 5 shown in FIG. 1 includes an Offner relay mirror 5 ahaving a concave face and a Schlieren filter 5 b in the form of a convexmirror which are disposed in an opposing relationship to each other asseen in FIG. 2.

As seen in FIG. 2, the laser light synthesized by the second colorsynthesis filter 24 b is illuminated on the Offner relay mirror 5 ahaving a concave face. The concave Offner relay mirror 5 a reflects theilluminated light to the Schlieren filter 5 b having a convex face.

The Schlieren filter 5 b in the form of a convex mirror is disposed on aFourier plane of the concave Offner relay mirror 5 a and has a radius ofcurvature having a ratio of 1:2 to that of the concave Offner relaymirror 5 a. The 0th order light, +second order light, −second orderlight, or the +first order light, −first order light, and otherdiffracted lights of higher numbered orders reflected by the concaveOffner relay mirror 5 a are converged at individually differentpositions on the convex face of the Schlieren filter 5 b. The Schlierenfilter 5 b removes the diffracted lights other than the ±first orderlights and introduces only the ±first order lights to the lightdiffusion section 7.

FIGS. 8A, 8B and 8C illustrate a principle of the spatial filter 5.

Referring first to FIG. 8A, the spatial filter 5 is represented as alens 51 representative of a function of the Offner relay mirror 5 a andhas a reflecting surface 52 representative of a function of theSchlieren filter. Reference character X denotes the Fourier plane of thelens 51.

Diffracted lights of individual numbered orders illuminated on the lens51 are converged on the reflecting surface 52 provided on the Fourierplane X. For example, the 0th order light is converged at a position b,and the +first order light and the −first order light are converged atpositions a and c, respectively.

As seen in FIG. 8C, an opening 55 is provided at the position b on thereflecting surface 52 and passes the 0th order light therethrough. Aregion 56 a and another region 56 b of the reflecting surface 52corresponding to the positions a and c reflect the +first order lightand the −first order light, respectively.

The ±second order lights or the ±third order lights and the diffractedlights of the other higher numbered orders are converged at positions onthe opposite outer side positions with respect to the positions a and c,that is, a region 57 a or 57 b. As seen in FIG. 8C, an opening isprovided at each of the regions 57 a and 57 b and the openings pass suchdiffracted lights of the high numbered orders therethrough.

Since the convex reflecting surface of the Schlieren filter 5 b isconfigured such that it reflects the necessary diffracted lights butpasses therethrough the unnecessary diffracted lights through theopenings provided at the converging positions of the unnecessarydiffracted lights, the spatial filter 5 extracts only the ±first orderlights. The thus extracted ±first order lights are reflected to theOffner relay mirror 5 a. The spatial filter 5 thus serves as a displaylight separation means for separating displaying light andnon-displaying light as described above.

Referring back to FIG. 2, the concave Offner relay mirror 5 a reflectsthe laser light synthesized by the second color synthesis filter 24 b ata reflection angle smaller than that of a reflecting mirror in the formof a flat plate to the Schlieren filter 5 b. The convex Schlieren filter5 b reflects the ±first order lights at reflection angles greater thanthat of a reflecting mirror in the form of a flat plate to the Offnerrelay mirror 5 a. The concave Offner relay mirror 5 a reflects the±first order lights at reflection angles smaller than that of areflecting mirror in the form of a flat plate to a mirror 50.

The ±first order lights can be extracted without any aberration by thearrangement of the concave Offner relay mirror 5 a and the convexSchlieren filter 5 b.

FIG. 8B indicates focal positions of the diffracted lights as viewed ina ZZ′ direction of FIG. 8C. As seen in FIG. 8B, although the convergingpoints of the diffracted lights of the different numbered orders areoffset from each other in the ZZ′ direction, they are not offset fromeach other in a direction perpendicular to the ZZ′ direction.

Referring back to FIG. 2, the mirror 50 deflects the modulated lightstoward the light diffusion section 7. Referring to FIGS. 9A and 9B, thelight diffusion section 7 diffuses the laser light introduced theretofrom the mirror 50 into a parallel light having a great width in sideelevation (FIG. 9A) and having a small width in top plan (FIG. 9B). Thediffused linear laser light is introduced into the projection lens 25.Referring back to FIG. 2, the projection lens 25 projects the diffusedlinear laser light onto the scanning mirror 26. Here, the mirror 50serves as a second deflecting mirror, and the light diffusion section 7serves as a second shaping means while the projection lens 25 serves asa projection optical system.

The scanning mirror 26 is formed from, for example, a galvano mirror andprojects the linear laser light forwardly onto the screen 8 to form aone-dimensional image formed from a train of pixel elements. Further,the scanning mirror 26 rotates in response to an image signal and scanssuch a one-dimensional image on the screen 8 to form a two-dimensionalimage. Thus, the scanning mirror 26 serves as a scanning means.

According to the present embodiment, the image display apparatus in theform of a projector which uses a GLV device can be formed compact.Further, the image display apparatus can form a display color of a highquality through color synthesis and remove unnecessary diffracted lightsefficiently. Consequently, since the diffracted light to be used forimage display includes minimized noise, the image display apparatus candisplay a color video image of a high quality.

Second Embodiment

An image display apparatus according to a second embodiment of thepresent invention has a basic configuration similar to that of the imagedisplay apparatus of the first embodiment described hereinabove withreference to FIGS. 1 and 2. Thus, the reference numerals used for thedescription of the image display apparatus of the first embodiment aresimilarly used for the present embodiment although the overlappingdescription is omitted.

Since illumination conditions of the laser light sources 21R, 21G and21B have some ununiformity and modulation characteristics of the pixelelements of the GLV devices 23R, 23G and 23B have some dispersion, animage displayed has some ununiformity in color and luminance. The imagedisplay apparatus of the present embodiment can detect and correct suchununiformity to display a video image of a higher picture quality.

If the illumination conditions are uniform and the modulationcharacteristics of the pixel elements of the GLV devices 23R, 23G and23B have no dispersion, then the image display apparatus describedhereinabove can display an ideal video image if an image signal isinputted to the driving circuits for the GLV devices 23R, 23G and 23B tooperate the GLV devices 23R, 23G and 23B.

Actually, however, the characteristics of the GLV devices 23R, 23G and23B themselves and the characteristics of the driving circuits for themhave some dispersion. Therefore, they do not operate uniformly inresponse to incoming light, and the luminance on the screen becomesununiform and a horizontal stripe or stripes appear on the screen.

Further, as regards the illumination conditions, even if theillumination optical systems are optimized, it is difficult to make theillumination conditions uniform over all of the GLV devices, which givesrise to appearance in ununiformity in luminance and color display on thescreen.

FIGS. 10A to 10D are sectional views in a transverse direction of theGLV device 23 shown in FIG. 3.

In FIGS. 10A and 10C, six ribbon electrodes 10 a, 11 a, 10 b, 11 b, 10 cand 11 c form one pixel element of the GLV device 23. Adjacent ribbonelectrodes 10 d, 11 d and 10 e form an adjacent pixel element. Similarlyas in FIGS. 3 to 5, the ribbon electrodes 10 a, 10 b, 10 c, 10 d and 10e are movable ribbon electrodes while the ribbon electrodes 11 a, 11 b,11 c and 11 d are fixed ribbon electrodes.

FIGS. 10B and 10D illustrate luminance distributions of one-dimensionalimages formed on the screen 8 and corresponding to operation conditionsof the GLV device shown in FIGS. 10A and 10C, respectively.

FIG. 10A illustrates a dispersion in position of the ribbon electrodesof the GLV device when no driving voltage is applied. FIG. 10Billustrates a luminance distribution of a one-dimensional image on thescreen 8 corresponding to the GLV device in the state of FIG. 10A whenno driving voltage is applied to the movable ribbon electrodes.

As seen from FIG. 10A, even if no driving voltage is applied, the ribbonelectrodes 10 a and 10 d are not positioned in the same plane as that ofthe other ribbon electrodes and have vertical offsets ΔD1 and ΔD2,respectively. Consequently, the pixel elements of the GLV device have aunique dispersion in modulation characteristic.

When no driving voltage is applied, if illumination light is introducedinto the GLV device 23, then ideally no diffracted light is produced andblack is displayed on the screen 8. However, due to the vertical offsetsof the ribbons of the GLV device, some diffracted lights are produced,and unintended bright spots are displayed at positions i and j of thedark screen of the screen 8 corresponding to the ribbon electrodes 10 aand 10 d, respectively. Further, the scanning mirror 26 scans theone-dimensional image, and thereupon, horizontal stripes are formed onthe screen 8 and decrease the contrast of the screen.

FIG. 10C illustrates a dispersion in position of the ribbon electrodesof the GLV device when a driving voltage is applied. FIG. 10Dillustrates a luminance distribution of a one-dimensional image on thescreen 8 corresponding to the GLV device in the state illustrated inFIG. 10C.

As seen in FIG. 10C, when a driving voltage is applied, the ribbonelectrodes 10 c and 10 d are moved to unintended positions and haveoffsets of ΔZ1 and −ΔZ2 from their desired positions, respectively. Onthe screen 8, the luminances at positions k and l corresponding to theribbon electrodes 10 c and 10 d do not coincide with desired luminancesand have some dispersion in luminance. The scanning mirror 26 similarlyscans the one-dimensional image, and thereupon, horizontal stripes areformed on the screen 8 and deteriorate the picture quality.

FIG. 11 illustrates the ununiformity in color and luminance of aone-dimensional image on the screen 8 caused by the ununiformity inillumination condition involved in the lasers 21R, 21G and 21B of red(R), green (G) and blue (B). Since the illumination conditions areununiform among the GLV devices 23R, 23G and 23B, the ununiformity inluminance and color display appears on the screen, and horizontalstripes in color and luminance are produced by scanning of the scanningmirror.

In order to eliminate such ununiformity in luminance and color on thescreen caused by a dispersion or instability in characteristic unique tothe image elements and the light sources as described above, in thepresent embodiment, a light detection apparatus and a circuit forperforming arithmetic operation for correction are provided. Thus, theununiformity in luminance and color is measured and corrected inadvance, and results of the optimization obtained through themeasurement and correction are stored as a data table into a memory andused for later image display.

FIG. 12 shows an example of a configuration of the image displayapparatus 101 of the present embodiment.

FIG. 12 shows an example of arrangement of the components describedabove of the image display apparatus 101.

Referring to FIG. 13, in the image display apparatus 101 shown, anoptical system 101 a includes a light detection apparatus 15 in additionto the light source section 2, illumination optical system 3, opticalmodulation section 4, spatial filter (SFT) 5, light projection section 6and screen 8.

Referring to FIG. 12, the signal processing section 9 includes a testsignal production section 31, a detection signal processing section(DSP) 32 and a correction circuit section 33 in addition to the videosignal input processing section (VSIP) 27, element driving circuitsection (DRV) 28, system control section (CPU) 29 and scan controlsection (SCMCNT) 30. The test signal production section 31 applies atest driving voltage to the GLV devices 23R, 23G and 23B to detect theununiformity in color and luminance displayed. The detection signalprocessing section 32 processes a signal detected by the light detectionapparatus 15. The correction circuit section 33 determines an optimumdriving voltage with which the ununiformity in color and luminance to bedisplayed is to be corrected based on the detection signal.

The video signal input processing section (VSIP) 27 serves as an initialdriving signal production circuit.

The element driving circuit section (DRV) 28 serves as a drivingcircuit.

The test signal production section 31, detection signal processingsection (DSP) 32 and correction circuit section 33 serve as a correctionsection.

In the present embodiment, the light detection apparatus 15 measuresmodulated lights emitted from the pixel elements of the GLV devices todetermine modulation characteristics. Further, the light detectionapparatus 15 detects the ununiformity in luminance and color displayedcaused by a dispersion in modulation characteristic and the luminanceconditions. As seen in FIG. 12, the light detection apparatus 15includes a reflecting mirror 16, and an optical sensor 17 which may beformed from, for example, an integrating sphere or a CCD unit. Further,a lens 18 for converging deflected laser light is interposed between thereflecting mirror 16 and the optical sensor 17 as seen in FIG. 13.

The reflecting mirror 16 deflects the modulated light emitted from theprojection lens 25 toward the optical sensor 17.

Where, for example, an integrating sphere is used, the optical sensor 17reflects the light inputted thereto in the inside of the integratingsphere so that it may not leak to the outside of the integrating sphereto collect all of the inputted light and measure the energy of thelight, that is, the amount of the incoming light.

The reflecting mirror 16 is positioned at the position shown in FIG. 13,for example, only when the display ununiformity is to be measured inadvance to change the light path. When an image is to be displayedactually, however, the reflecting mirror 16 is removed to restore theordinary light path.

The light detection apparatus 15 serves as a measuring means.

Accordingly, the image display apparatus 101 operates in the followingmanner to display a two-dimensional color image.

First, the ununiformity in luminance and color displayed is measured andcorrected in advance.

FIG. 14 is a flow chart illustrating the operation for measurement andcorrection by the image display apparatus 101.

Step S11:

A measurement of the ununiformity in display luminance and color of theimage display apparatus 101 is performed.

Step S12:

The laser light sources 21R, 21G and 21B successively illuminate laserlight upon the GLV devices 23R, 23G and 23B while the test signalproduction section 31 applies a test signal successively changing, forexample, from a predetermined minimum voltage to a predetermined maximumvoltage as a driving signal to all of those pixel elements of the GLVdevices on which the laser light is illuminated. The light detectionapparatus 15 individually measures the amounts of modulated lightsemitted from the individual pixel elements.

Step S13:

The detection signal processing section 32 performs initial processessuch as gain adjustment and A/D conversion for the signal of modulatedlight from each of the pixel elements measured by the light detectionapparatus 15. The correction circuit section 33 uses the amount ofmodulated light from each of the pixel elements measured by the lightdetection apparatus 15 to analyze and detect the ununiformity inluminance and color of image display by the pixel element to determinean optimum driving voltage to be applied to the pixel element of eachcolor with respect to the predetermined initial driving voltage. Thecorrection circuit section 33 produces a data table of such determinedoptimized driving voltage data and stores the data table into the memoryof the image display apparatus 101.

When an image is to be displayed actually, the stored data table of thedriving voltages is used to apply the driving voltages to the individualpixel elements of the GLV devices.

A succeeding flow of image display is similar to that in the firstembodiment.

Now, a method of measuring and correcting the ununiformity in luminanceand color to be displayed in the present embodiment is described.

FIG. 15 shows a detailed configuration of the signal processing section9.

Referring to FIG. 15, the video signal input processing section 27includes an inverse γ correction circuit (IGC) 69 and a color spaceconversion circuit (CSC) 70 and processes a video image signal VIDEO inthe form of RGB signals obtained, for example, by conversion from colordifference signals YCbCr (YPbPr).

The inverse γ correction circuit 69 converts a non-linear characteristic(γ characteristic) applied to the RGB signals into a linearcharacteristic through an inverse gamma correction process.

The color space conversion circuit 70 performs a color space conversionprocess for the RGB signals in order for the RGB signals to correspondto the color reproduction range of the illumination light sources. Thevideo image signal VIDEO processed in this manner is inputted to thecorrection circuit section 33.

The detection signal processing section 32 includes a gain adjustmentcircuit (GM) 61 and an A/D (analog to digital) conversion circuit 62 andperforms an initial process for a signal of modulated light from each ofthe pixel elements measured by the optical sensor 17.

The gain adjustment circuit 61 corrects the difference in detectionsensitivity of the optical sensor 17 to the laser lights of differentwavelengths emitted from the laser light sources 21R, 21G and 21B basedon the detected modulated light signals.

The A/D conversion circuit 62 converts each of the detection signalsafter the correction into a digital signal. The detection data obtainedby the conversion is successively stored into a memory 63 in thecorrection circuit section 33.

The correction circuit section 33 includes a memory 63, a correctionvalue calculator (CCAL) 64, a data table storage section (LUT) 65 and aselection circuit (SEL) 66.

A measurement of the modulated lights is performed for all of the pixelelements of the GLV devices 23R, 23G and 23B, and resulting data arecumulatively stored into the memory 63. Thereafter, the correction valuecalculator 64 uses the measurement data of each of the individual pixelelements to determine a modulation characteristic of the pixel elementto derive an illumination profile of each of the GLV devices. Then, thecorrection value calculator 64 determines an optimum driving voltage tobe applied to each of the pixel elements of the GLV devices so that thepixel element exhibit no ununiformity in luminance and color in theillumination profile of the GLV device with respect to a predeterminedinitial driving voltage. Then, the correction value calculator 64prepares a data table for such optimized driving voltage data determinedin this manner and stores the data table into the data table storagesection 65.

When an image is to be displayed, the corrected driving signals storedin the data table storage section 65 are outputted to the elementdriving circuit section 28 to display an image.

When the display ununiformity is to be measured and corrected prior todisplay, the selection circuit 66 selects the test driving signalsoutputted from the test signal production section 31. However, when animage is to be displayed, the selection circuit 66 selects the correcteddriving signals stored in the data table storage section 65.

Processing of the correction value calculator 64 is hereinafterdescribed in detail.

The element driving circuit section 28 includes a D/A (digital toanalog) conversion circuit 67 and a driving circuit (DRVC) 68. The D/Aconversion circuit 67 converts digital driving signals outputted fromthe correction circuit section 33 into analog signals. The drivingcircuit 68 applies the analog signals to ribbon electrodes ofpredetermined pixel elements of the GLV devices 23R, 23G and 23B. TheGLV devices 23R, 23G and 23B operate in response to the driving signalsto modulate the laser lights emitted from the red laser 21R, green laser21G and blue laser 21B, respectively.

The system control section 29 controls operation timings of thecomponents of the signal processing section 9 described above.

Now, a method executed at step S12 of FIG. 14 for detecting theununiformity in luminance and color displayed is described.

FIG. 16 is a flow chart illustrating the process of measuring theununiformity in luminance and color displayed.

Step S21:

Before an image is displayed, the reflecting mirror 16 and the opticalsensor 17 are placed in position to measure the ununiformity inluminance and color in advance.

Step S22:

One of the laser light sources, for example, the red light source 21R,is turned on to emit a laser beam. The laser beam thus emitted is shapedinto a linear shape by the illumination optical system 22R andilluminates the entire GLV device 23R.

Step S23:

The modulation characteristic, that is, the relationship between thedriving voltage and the luminance of modulated light, of all of thepixel elements of the red GLV device 23R is successively measured.

In order to measure the modulation characteristic of a certain pixelelement, test signals produced by the test signal production section 31are inputted as driving voltage signals to the driving circuits for thepixel element of the object of measurement through the selection circuit66 so as to be applied to the ribbon electrodes of the pixel element ofthe object of measurement.

FIG. 17A illustrates a waveform of a test signal produced by the testsignal production section 31.

The test signal produced by the test signal production section 31 is atriangular signal whose signal level (relative value) gradually variesor increases like 0, 1, . . . , 254, 255 as time passes as seen in FIG.17A.

The pixel element of the object of measurement operates in response tothe driving signal illustrated in FIG. 17 whose level (relative value)varies like 0, 1, . . . , 254, 255 to modulate the red laser lightinputted thereto and emits the modulated light in the form of diffractedlight having an intensity responsive to the level.

The test signal illustrated in FIG. 17A serves as a first test signal.The range of variation of the signal level from the minimum value of 0to the maximum value of 255 is referred to as a first variation range.

Where the laser light source 21R illuminates the entire red GLV device23R, it serves as a first illumination means.

The optical sensor 17 measures the intensity of modulated light inputtedthereto, converts the measured intensity of the modulated light into anelectric signal and outputs the electric signal.

The intensity of the modulate light depends upon the offset betweenribbon electrodes per one pixel in the GLV device 23R. The offset arisesfrom a dispersion of the unique surface position of each ribbonelectrode and a dispersion of the surface position of each ribbonelectrode which depends upon the accuracy of the driving voltage.

FIG. 17B illustrates the levels of the output signal which correspond tothe intensities of modulated light measured by the optical sensor 17with respect to the individual levels of the applied test signal, thatis, a modulation characteristic.

As seen from FIG. 17B, while the voltage value of the test signal varieslinearly, the intensity of the modulated light does not vary linearly.Where the level of the driving voltage is low, the intensity of themodulated light is zero, and after the level of the driving voltageexceeds a certain value, the intensity of the modulated light exhibits asudden increase.

FIG. 18 illustrates a variation of the sensitivity of the optical sensor17 with respect to the wavelength. As seen in FIG. 18, the opticalsensor 17 exhibits a different measurement sensitivity to light of adifferent wavelength. In other words, the output level of the opticalsensor 17 varies with respect to incoming light having an equalintensity but having a different wavelength. Accordingly, when themodulation characteristic of the pixel elements of the GLV devices ismeasured with respect to laser lights of the three colors of R, G and B,it is necessary to normalize the results of measurement.

In order to correct wavelength sensitivity differences of the sensor,the wavelength sensitivities of the sensor are measured in advance todetermine normalization coefficients fr, fg and fb for the wavelengthsof the lights to be emitted from the laser light sources 21R, 21G and21B. Then, the outputs of the optical sensor 17 when the laser lightsources 21R, 21G and 21B are lit are multiplied by the coefficients fr,fg and fb, respectively, to adjust the gains of the optical sensor 17 toeach other for the individual light sources.

As a result, if a predetermined driving voltage is applied to a certainpixel element and illumination lights of the three colors of R, G, and Bhaving an equal intensity are illuminated upon the pixel element, thenthe outputs (voltage values) of the optical sensor 17 exhibit an equalvalue.

The gain adjustment circuit 61 of the detection signal processingsection 32 shown in FIG. 15 performs the gain adjustment processdescribed above.

The A/D conversion circuit 62 converts an analog signal outputted fromthe gain adjustment circuit 61 into digital data and thus storestotaling 256 resulting data into the memory 63 of the correction circuitsection 33. The 256 data represent a modulation characteristic of thepixel element of the object of measurement.

The levels of the output signal of the optical sensor 17 illustrated inFIG. 17B represent a result of measurement of the modulationcharacteristic of a pixel element. For example, when 1,080 pixels are tobe displayed, the red GLV device 23R repetitively performs such ameasurement as described above by 1,080 times to measure the modulationcharacteristic similarly for the 1,080 pixels of the GLV device 23Rsimilarly and stores 1,080×256 data obtained by the measurement into thememory 63.

When a measurement is performed for a predetermined one pixel element,the other pixel elements are masked so that they may not be illuminatedby the illumination light.

Step S24:

For example, after the modulation characteristic of all of the pixelelements of the red GLV device 23R is measured, the laser light source21R is turned off.

Step S25:

Similar processing is successively performed for the laser light sources21G and 21B to measure the modulation characteristic of all of the pixelelements of the GLV devices 23G and 23B.

Also measurement data of the modulation characteristic of all of thepixel elements of the GLV devices 23G and 23B are successively storedinto the memory 63.

The modulation characteristic data of all of the pixel elements of theGLV devices 23R, 23G and 23B are represented collectively by functionsIr(v, x), Ig(v, x) and Ib(v, x). Here, the variable v represents thedriving voltage, and the variable x represents the position of eachpixel element and is used to identify the pixel element. The charactersr, g and b represent three colors of red, green and blue, respectively.

FIG. 19 illustrates an example of the modulation characteristics Ir(v1,x), Ig(v1, x), Ib(v1, x) of the GLV devices 23R, 23G and 23B at acertain level v1 of the test signal and illustrates the variations ofthe intensity of the modulated lights emitted from the individual pixelelements of the GLV devices.

As seen from FIG. 19, the intensities of the modulated lights varysignificantly along the direction of arrangement of the pixel elementsof the GLV devices 23R, 23G and 23B.

The intensities of the modulated lights emitted from the GLV devices23R, 23G and 23B depend upon the dispersion in position of the ribbonelectrodes of the pixel elements and the intensity of the laser lightsources 21R, 21G and 21B. Particularly, the intensity of the illuminatedlight from each of the laser light sources varies among all of thepixels of each GLV device and is not uniform. Further, the intensitydistributions of the illumination lights vary as time passes and withrespect to the temperature.

The modulation characteristic data of all of the pixel elements of theGLV devices 23R, 23G and 23B stored in the memory 63 are analyzed by thecorrection value calculator 64 included in the correction circuitsection 33 to eliminate the ununiformity in luminance and colordisplayed.

FIG. 20 shows a configuration of the correction value calculator 64.

The correction value calculator 64 includes a voltage/luminanceconversion section (L/V) 81, a luminance distribution analysis section(LDA) 82, an ideal modulation characteristic function production section(IVO) 83, a multiplier 84, correction table production sections (CTG) 85a, 85 b and 85 c, and data table storage sections (LUT_R, LUT_G, LUT_B)86 a, 86 b and 86 c. The voltage/luminance conversion section 81converts the values of the modulation characteristics Ir(v, x), Ig(v,x), Ib(v, x) of the GLV devices 23R, 23G and 23B from voltage valuesinto luminance values IYr(v, x), IYg(v, x), IYb(v, x). The luminancedistribution analysis section 82 analyzes the luminance functions IYr(v,x), IYg(v, x), IYb(v, x). The ideal modulation characteristic functionproduction section 83 produces a desired modulation characteristicfunction. The correction table production sections 85 a, 85 b and 85 cperform correction of a driving signal to produce a correction datatable. The correction data tables for the driving signals from thecorrection table production sections 85 a, 85 b and 85 c are writteninto the data table storage sections 86 a, 86 b and 86 c, respectively.

Now, operation of the correction value calculator 64 is described withreference to a flow chart of FIG. 21.

Step S31:

The modulation characteristics Ir(v, x), Ig(v, x), Ib(v, x) of the GLVdevices 23R, 23G and 23B are measured with respect to the R, G and Blaser light sources and stored into the memory 63. Thereafter, thecorrection circuit section 33 processes and corrects the measurementdata.

Step S32:

The measured modulation characteristics Ir(v, x), Ig(v, x), Ib(v, x) ofthe GLV devices 23R, 23G and 23B are voltage values, and thevoltage/luminance conversion section 81 included in the correction valuecalculator 64 converts the voltage values into luminance values.

More particularly, in order to realize target white light, mixture ratiovalues Rc, Gc and Bc are determined first.

For example, three stimulus values of the three primary colors of R, Gand B are represented by R(Xr, Yr, Zr), G(Xg, Yg, Zg) and B(Xb, Yb, Zb),respectively, and the three stimulus values of white are represented by(Xw, Yw, Zw). As a result, the relationship between the mixture amountsRc, Gc, Bc of the three primary colors and the three stimulus values forrealizing the white is defined by the following expression (1):$\begin{matrix}{\begin{matrix}X_{w} \\Y_{w} \\Z_{w}\end{matrix} = \begin{matrix}X_{r} & X_{g} & X_{b} & R_{c} \\Y_{r} & Y_{g} & Y_{b} & G_{c} \\Z_{r} & Z_{g} & Z_{b} & B_{c}\end{matrix}} & (1)\end{matrix}$

The three stimulus values of the R, G, B laser light sources used in thepresent embodiment and the three stimulus values of the white (colortemperature 6,500 K) have such values, for example, as given below:

R(0.4121, 0.1596, 0.0000),

G(0.1891, 0.8850, 0.0369),

B(0.3089, 0.0526, 1.7209), and

W(0.9505, 1.0000, 1.0890).

The mixture amounts of the three primary colors of R, G and B forrealizing the white are determined as given by the following expression(2) by substituting the values above into the expression (1) givenhereinabove: $\begin{matrix}{\begin{bmatrix}0.9505 \\1.0000 \\1.0890\end{bmatrix} = {\begin{bmatrix}0.4121 & 0.1891 & 0.3089 \\0.1596 & 0.8850 & 0.0526 \\0.0000 & 0.0369 & 1.7209\end{bmatrix}\begin{bmatrix}R_{c} \\G_{c} \\B_{c}\end{bmatrix}}} & (2) \\{\begin{bmatrix}R_{c} \\G_{c} \\B_{c}\end{bmatrix} = {{\begin{bmatrix}0.4121 & 0.1891 & 0.3089 \\0.1596 & 0.8850 & 0.0526 \\0.0000 & 0.0369 & 1.7209\end{bmatrix}^{- 1}\begin{bmatrix}0.9505 \\1.0000 \\1.0890\end{bmatrix}} = \begin{bmatrix}1.4648 \\0.8292 \\0.6510\end{bmatrix}}} & (3)\end{matrix}$

The mixture amounts above represent a ratio of laser powers necessary torealize the white of the color temperature of 6,500 K with the luminanceY=1 using the three primary colors having the three stimulus valuesgiven above. In particular, Rc:Gc:Bc=1.4648:0.8292:0.6510.

The results Ir(v, x), Ig(v, k), Ib(v, k) of the measurement of themodulated light amounts [W] of the colors by the optical sensor 17 areillustrated in FIG. 19.

The luminances of the white which can be realized where the modulatedlights emitted from such GLV devices as described above are representedby Ywr, Ywg, and Ywb and can be detected in accordance with thefollowing expressions (4):Ywr=Ir(v,x)/RcYwg=Ig(v,x)/GcYwb=Ib(v,x)/Bc  (4)

As described hereinabove, the optical sensor 17 has such a wavelengthsensitivity as seen in FIG. 18. Further, the optical sensor 17 does notexhibit a measurement efficiency of 100% because of a geometricalcondition. Therefore, an effect of them must be canceled. Moreparticularly, luminance conversion coefficients Kr, Kg, Kb which reflecta variation in measured amount by the light receiving area or thewavelength sensitivity of the optical sensor 17 are determined inadvance, and the luminance functions Ywr, Ywg, Ywb are corrected bymultiplying them by the luminance conversion coefficients Kr, Kg, Kb,respectively.

Accordingly, the luminances IY of the white which can be realized afterthe correction are given by the following expression (5):IYr=Kr×Ywr=Kr×Ir(v,x)/Rc(lumen)IYg=Kg×Ywg=Kg×Ig(v,x)/Gc(lumen)IYb=Kb×Ywb=Kb×Ib(v,x)/Bc(lumen)  (5)

FIG. 22 illustrates luminance characteristics (or luminance profiles,that is, relationships between the luminance and the pixel position)IYr, IYg and IYb obtained by the voltage/luminance conversion section 81as a result of such processing of the distributions (light amount-pixelposition) of the modulation characteristics illustrated in FIG. 19 whenthe driving voltage v is v=v1.

Step S33:

The luminance distribution analysis section 82 analyzes the luminancecharacteristics (luminance-pixel position) IYr, IYg, IYb to search for acommon minimum value IY0 of the luminance characteristics IYr(v, x),IYg(v, x), IYb(v, x) for the driving voltages v. Then, the correctioncircuit section 33 performs correction of the value of the searched outminimum value IY0 to determine the maximum luminance IYmax of the whitewhich can be realized.

This is because a pixel element which cannot realize a luminance of thewhite higher than the minimum value IY0 is included in the GLV devices23R, 23G and 23B without fail.

In FIG. 22, the common minimum value IY0 to the luminancecharacteristics IYr(v, x), IYg(v, x), IYb(v, x) is given by the minimumvalue of the luminance characteristic IYb(v, x). In other words, theluminance characteristic IYb(v, x) becomes a constraint condition torealize the white, and the minimum value IY0 of the luminancecharacteristic IYb(v, x) becomes a maximum luminance IYmax of the whitewhich can be realized.

Step S34:

As described hereinabove, owing to the image inputting apparatus, thevideo image signal VIDEO has a unique γ characteristic, that is, wherethe input signal is represented by x (0<x<1) and the output signal isrepresented by y (0<y<1), the relationship of y=xγ is satisfied. Forexample, in the NTSC television system, γ=2.2.

As a result, the pixel elements of the GLV devices 23R, 23G and 23B havean ideal modulation characteristic in accordance with the γcharacteristic of the video image signal VIDEO. Where the modulationcharacteristics of the GLV devices 23R, 23G and 23B in accordance withthe γ characteristic of the video image signal VIDEO are represent by afunction IV(t), an ideal modulation characteristic IT(v) of all of thepixel elements is the product of the modulation characteristic IV(t) andthe maximum luminance IYmax of the white determined as describedhereinabove. In other words, IT(v)=IYmax×IV(v). The ideal modulationcharacteristic IT(v) is hereinafter referred to as target modulationcharacteristic. The modulation characteristic IV(t) in accordance withthe γ characteristic can be designated by a user.

In the correction value calculator 64, the luminance distributionanalysis section 82 outputs the maximum luminance IYmax of the whitewhich can be realized, and the ideal modulation characteristic functionproduction section 83 outputs the ideal modulation characteristicfunction IV(t) designated by the user. The multiplier 84 multiplies thefunction IYmax and the function IV(t). A result of the multiplicationmakes a target modulation characteristic IT(v).

FIG. 23 illustrates an example of the target modulation characteristicIT(v) determined in this manner.

Step S35:

The correction table production sections 85 a, 85 b and 85 c performcorrection of the driving signals and generate a correction table of thedriving signals for the individual illuminations of R, G and B and forthe individual pixels based on the target modulation characteristicIT(v) calculated as described above and illustrated in FIG. 23 and theluminance (modulation) characteristics IYr(v, x), IYg(v, x), IYb(v, x)(FIGS. 17B and 19) of the individual pixels actually measured so thatthe ununiformity in luminance and color may be eliminated.

FIGS. 24A and 24B illustrate a method of correcting the ununiformity indisplay in the present embodiment.

FIG. 24A illustrates the target modulation characteristic IT(v)calculated as described above, and FIG. 24B illustrates the luminance(modulation) characteristic IYr(v), IYg(v) or IYb(v) actually measured.In FIGS. 24A and 24B, the axis of abscissa indicates the driving voltageand the axis of ordinate indicates the luminance of a modulated light.

In order to correct the ununiformity in display, the correction tableproduction sections 85 a, 85 b and 85 c determine a corresponding targetluminance value Y on a curve of the target modulation characteristicIT(v) shown in FIG. 24A to a predetermined initial driving voltage Vinto be applied to each pixel element when no ununiformity in displayexists.

Then, the correction table production sections 85 a, 85 b and 85 cdetermine, for each pixel, a driving voltage Vout to be applied in orderto generate the target luminance value Y on a curve of a measuredmodulation characteristic, for example, on a curve of the luminancecharacteristic IYr(v).

Driving voltages Vout_n, Vout_m, Vout_l, . . . for the pixel elements N,M, L, . . . for realizing the target luminance value Y are obtained inthis manner.

In particular, the driving voltages to be applied to the pixel elementsN, M and L with respect to the predetermined initial driving voltage Vinare corrected to Vout_n, Vout_m and Vout_l as seen in FIG. 25 so thatthe pixel elements N, M and L may display the same luminance value Y.

The corrected driving voltages for all of the pixel elements of the GLVdevices 23R, 23G and 23B obtained in this manner are written into thedata table storage sections 86 a, 86 b and 86 c, respectively. Thecorrection process is completed thereby.

When an image signal is inputted later, driving signals are successivelycorrected for each pixel element and for each driving signal by the datatable storage sections 86 a, 86 b and 86 c to correct the ununiformityin luminance and color, and consequently, a video image of a highpicture quality is outputted.

FIG. 26 illustrates a luminance profile after the ununiformity inluminance and color is corrected in contrast with FIG. 22.

As seen in FIG. 26, after the corrected driving voltages are applied,the luminance profiles IYr, IYg and IYb of the laser light sources 21R,21G and 21 B become equal to each other, and the white of the colortemperature of 6,500 K (IYb lumen) can be realized correctly.

With the present embodiment, since the GLV devices are driven withcorrected driving signals whose ununiformity in illumination conditionand whose dispersion in pixel element characteristic are corrected foreach pixel, a video image of a high picture quality free from theununiformity in luminance and color on a screen can be provided.

Third Embodiment

An image display apparatus according to a third embodiment of thepresent invention has a basic configuration similar to that of thesecond embodiment described hereinabove with reference to FIGS. 12, 13and 15. However, in the present embodiment, the method of correcting theununiformity in color and luminance is different from that in the secondembodiment. Consequently, the correction value calculator forcalculating a correction value for a driving voltage is different fromthat of the correction value calculator 64 in the second embodiment. Thecorrection value calculator in the present embodiment is denoted byreference character 64 b.

In the present embodiment, the dispersion (which does not include theununiformity in illumination condition) in modulation characteristic ofeach pixel element in the GLV devices 23R, 23G and 23B is measured inadvance, and the ununiformity in illumination condition of each of thelaser light sources 21R, 21G and 21B is measured immediately before theprojector is rendered operative. A correction data table for a drivingvoltage is produced based on results of the two measurements.

A unique offset between ribbon electrodes of a GLV device arises, forexample, from the instability of a manufacturing step or an error of adriving signal and is independent of a secular change or a temperaturevariation. Meanwhile, a light source is subject to a secular change or atemperature variation in terms of the ununiformity in illuminationcondition thereof, and there is the possibility that a result of ameasurement performed in advance may not be applied after time passes.Therefore, a method wherein they are measured independently of eachother, that is, a method wherein a modulation characteristic of a devicewhich does not include an influence of illumination is measured firstand then the ununiformity in illumination is measured immediately beforethe device is used can cope with a secular change of an operationcondition of a light source.

The figures used for the description of the image display apparatus ofthe first and second embodiments are similarly used for description ofthe image display apparatus of the present third embodiment althoughoverlapping description is omitted herein to avoid redundancy.

FIG. 27 is a flow chart illustrating a general flow of processing whenthe image display apparatus of the present embodiment measures thedispersion in modulation characteristic of the pixel elements and theununiformity in illumination condition to perform correction of adriving voltage.

Individual steps of the process illustrated in FIG. 27 are describedbelow.

Step S41:

For example, a separate adjustment apparatus is used in advance toilluminate laser light upon the individual pixel elements of the GLVdevices 23R, 23G and 23B to measure the modulation characteristic (whichdoes not include the ununiformity in illumination condition) of theindividual pixel elements.

Step S42:

Immediately before an image is displayed by the image display apparatusof the present embodiment, the laser light sources 21R, 21G and 21B ofthe image display apparatus are successively turned on to successivelyilluminate the GLV devices 23R, 23G and 23B. In particular, the testsignal production section 31 successively applies a high level testsignal as a driving signal to the individual pixel elements of the GLVdevices, and the light detection apparatus 15 measures the amount ofmodulated light emitted from the pixel element to which the test signalis applied to obtain the ununiformity in illumination condition (anillumination profile).

Step S43:

The correction circuit section 33 processes the measured modulationcharacteristics of the pixel elements and the illumination profiles todetermine optimum driving voltages to be applied to the individual pixelelements for the different colors with respect to a predeterminedinitial driving voltage. Then the correction circuit section 33 producesa data table of the determined optimized driving voltage data and storesthe data table into the memory.

Then, before an image is displayed, the stored driving voltage datatable is used to apply the optimized driving voltages to the individualpixel elements of the GLV devices.

A flow of later processing for the image display is similar to that inthe first and second embodiments.

FIG. 28 shows an example of a configuration of a modulation deviceadjustment apparatus 201 for measuring the modulation characteristic(which does not include the ununiformity in illumination condition) ofthe individual pixel elements of the GLV devices 23R, 23G and 23B inadvance.

The modulation device adjustment apparatus 201 includes a light source202, an illumination optical system 203, a mirror 204 a, another mirror204 b, a projection lens 206, a spatial filter 207, and an opticalsensor 217. The light source 202 includes R, G and B laser lightsources. The illumination optical system 203 shapes the laser lightsfrom the light source 202. The mirror 204 a deflects the laser lights soas to be inputted to a GLV device 205 for each pixel. The mirror 204 bdeflects modulated lights emitted from the pixel element upon which thelaser lights are illuminated. The projection lens 206 projects themodulated lights to form an image. The spatial filter 207 extracts firstorder diffracted lights included in the modulated lights but removesdiffracted lights of the other order numbers.

In the modulation device adjustment apparatus 201, the illuminationoptical system 203 shapes single-color laser lights emitted from thelight source 202 so that they may form dot-like beam spots andilluminates the beam spots on the GLV device 205 for each pixel. A testsignal illustrated in FIG. 17A is applied to the pixel element beingilluminated to modulate the incoming lights. The modulated lightsemitted from the pixel element are measured by the optical sensor 217.In particular, the optical sensor 217 measures the intensity of themodulated lights of the pixel element to determine a modulationcharacteristic of the pixel element. Here, it is assumed that there isno intensity variation of the illumination lights within the range ofthe one pixel.

The spatial filter 207 is similar to the spatial filter 5 describedhereinabove in connection with the first and second embodiments.Meanwhile, the GLV device 205 includes three GLV devices for red, greenand blue which are hereinafter referred to as GLV devices 205R, 205G and205B, respectively.

Though not shown, the modulation device adjustment apparatus 201includes a position fixation apparatus for fixing a GLV device to adjustthe illumination position for pixels, one by one.

The GLV device has a positioning mark provided thereon so that theoptimum positions when the GLV device is incorporated in the modulationdevice adjustment apparatus 201 and when it is incorporated in the imagedisplay apparatus may coincide with each other. When the modulationdevice adjustment apparatus 201 is used to perform a measurement, theposition of the GLV device relative to the illumination is adjusted inaccordance with the mark by the position fixation apparatus.

The light source 202 and the illumination optical system 203 serve as asecond illumination section.

Now, a method of measuring the modulation characteristic (which does notinclude the ununiformity in illumination condition) of the pixelelements in advance is described.

FIG. 29 is a flow chart illustrating a process of measuring themodulation characteristic (which does not include the ununiformity inillumination condition) of the pixel elements in advance.

Step S51:

For example, before the GLV device is incorporated into the projector,the modulation characteristic thereof including a driving circuitcharacteristic is measured. After the GLV device 205 is set and adjustedin position as described above, the optical sensor 217 is moved to animage forming position of a pixel of an object of measurement and ameasurement is started.

Step S52:

The light source 202, for example, the red laser light source, is turnedon to emit laser light. The laser light thus emitted is shaped by theillumination optical system 203 and illuminated upon the GLV device205R.

As described hereinabove, the representative dimensions of one pixelelemet (including six ribbon electrodes) of the GLV device 205 are suchthat the width is approximately 25 μm and the length is approximately200 to 400 μm. Accordingly, if the size of the beam spot to beilluminated upon one pixel element of the GLV device 205 is set to, forexample, 25 μm.times.500 μm, then the GLV device 205 can be illuminatedfor each single pixel.

The position fixation apparatus shifts the illumination position of thelight beam on the GLV device 205 and adjusts is to each pixel, one byone.

Step S53:

The modulation characteristic of the pixel elements of the GLV device205, that is, the relationship between the driving voltage and theluminance of the modulated light, is successively measured.

In order to measure the modulation characteristic of a pixel element, atest signal which successively varies as illustrated in FIG. 30A isinputted as a driving voltage signal to the driving circuit for thepixel element so as to be applied to the ribbon electrodes in a similarmanner as in the second embodiment.

The pixel element modulates the laser light inputted thereto and emitsdiffracted light (modulated light) of an intensity corresponding to thelevel of the driving voltage applied thereto.

The optical sensor 217 measures the intensity of the modulated lightemitted from the pixel element. FIG. 30B illustrates a modulationcharacteristic measured in this manner.

Then, the gain adjustment circuit 61 in the detection signal processingsection 32 described hereinabove in connection with the secondembodiment performs a gain adjustment process for the output signal ofthe optical sensor 217. Then, the A/D conversion circuit 62 converts ananalog signal outputted from the gain adjustment circuit 61 into digitaldata. Thus, a measured modulation characteristic formed from totaling256 data for one pixel element is stored into a memory 282 (FIG. 34) ofthe correction value calculator 64 b.

In order for the GLV device 205, particularly the GLV device 205R, todisplay, for example, 1,080 pixels, the measurement procedure describedabove is repetitively performed by 1,080 times with the position of thedetector shifted successively to measure the modulation characteristicof each of the 1,080 pixels of the GLV device 205R. The 1,080×256 dataobtained by the measurement are stored into the memory 282.

Step S54:

After the modulation characteristic of all of the pixel elements of, forexample, the GLV device 205R is measured, the lit red laser is turnedoff.

Step S55:

A similar process is performed also for the green laser light source andthe blue laser light source to measure the modulation characteristic ofall of the pixel elements of the GLV devices 205G and 205B.

Also the measured data of the modulation characteristic of all of thepixel elements of the GLV devices 205G and 205B are stored into thememory 282.

The modulation characteristic data of all of the pixel elements of theGLV devices 205R, 205G and 205B are collectively represented byfunctions Isr(v, x), Isg(v, x) and Isb(v, x), respectively. Here, thevariable v represents the driving voltage, and the variable x representsthe position of each pixel element and is used for identification of thepixel element. Reference characters r, g and b represent the primarycolors of red, green and blue, respectively.

FIG. 31 illustrates an example of the modulation characteristics Isr(v1,x), Isg(v1, x) and Isb(v1, x) of the GLV devices 205R, 205G and 205B ata certain level v1 of the test signal and illustrates variations of theintensity of modulated lights emitted from the pixel elements of the GLVdevices.

As seen from FIG. 31, the intensities of the modulated lights of the GLVdevices 205R, 205G and 205B exhibit significant variations along thedirection of arrangement of the pixel elements due to a dispersion inpixel element modulation characteristic.

The variations of the modulation characteristics Isr(v1, x), Isg(v1, x)and Isb(v1, x) shown herein arise from unique dispersions of the pixelelements and the driving circuits but include no influence of theillumination profile of the light source 202.

Subsequently, a method of detecting an illumination profile solelyimmediately before an image is displayed is described. In this instance,the GLV device is incorporated into the image display apparatus, and thelight detection apparatus 15 is provided in the image display apparatusas shown in FIG. 12 to measure the illumination profiles of the lightsources 21R, 21G and 21B arranged in the image display apparatus.

The illumination profiles measured here do not include an influence ofthe dispersions of the modulation characteristics (including aninfluence of the driving circuits) unique to the pixel elements.

However, while the modulation characteristic of a pixel element can bemeasured solely, it is not easy to measure an illumination profilesolely. This is because, if the entire GLV device is illuminated, thenan influence of the illumination ununiformity exists together with aninfluence of the dispersions of the modulation characteristics(including an influence of the driving circuits) unique to the pixelelements without fail. Accordingly, as far as the ununiformity indisplay by a pixel element exists, an illumination file cannot bemeasured solely.

However, a method of approximately measuring an illumination profilesolely is available.

As described hereinabove, the maximum displacement amount of a movableribbon electrode is λ/4. Here, λ is the wavelength of the incominglight. For example, in the R, G and B light sources used in the presentembodiment, λ=650 nm for red (R): λ=532 nm for green (G): and λ=460 nmfor blue (B). Therefore, for the illumination lights of red, green andblue, the maximum displacement amount λ/4 of the movable ribbon elementis 162.5 nm, 133 nm and 115 nm, respectively.

Meanwhile, the dispersion of the position of the ribbon electrodesurface by unevenness unique to the surface of the ribbon electrode andthe driving circuit normally is approximately several nm. Accordingly,where the movable ribbon element is displaced over the maximum distance,it is considered that the influence of the unevenness of the ribbonelectrode itself and the unevenness by the driving signal upon themodulation effect of the GLV device is sufficiently low and can beignored.

Accordingly, if a test signal whose level varies within the range of 240to 255 as seen in FIG. 32 is applied as a driving signal to a GLV deviceto operate the GLV device and the modulated light is measured by meansof the optical sensor 17, then an illumination profile of each pixelelement, that is, relationships Pr(x), Pg(x) and Pb(x) between theluminance and the pixel (position), can be measured.

Actually, where the test signal ranges from 240 to 255, the amount ofthe modulated light does not increase monotonously. Therefore, a maximumvalue of the luminance measured within the range of the test signal from240 to 255 is determined as a value of an illumination profile.

The test signal illustrated in FIG. 32A, whose level varies within therange of 240 to 255, serves as a second test signal which varies withina second range.

FIG. 33 is a flow chart illustrating a process of detecting anillumination profile solely immediately before an image is displayed.

Step S61:

Immediately before an image is displayed, the reflecting mirror 16 andthe optical sensor 17 shown in FIG. 12 are set in position to measure anillumination profile.

Step S62:

A laser light source, for example, the red laser light source 21R, isturned on. The laser light emitted from the red laser 21R then is shapedlinearly by the red illumination optical system 22R and illuminates theoverall GLV device 23R.

Step S63:

The intensity of the modulated light is measured for the individualpixel elements of the GLV device 23R.

To this end, the test signal production section 31 produces such a testsignal as illustrated in FIG. 32 and inputs the test signal as a drivingvoltage signal to the driving circuit for a pixel element of an objectof measurement through the selection circuit 66 so as to be applied tothe ribbon electrodes of the pixel element of the object of measurement.

The test signal illustrated in FIG. 32 has the level (relative value)which varies within the range from 240 to 255.

The pixel element of the object of measurement modulates the red laserlight inputted thereto, and the GLV device 23R emits the modulatedlight. The optical sensor 17 measures the intensity of the modulatedlight corresponding to each of the levels of the test signal.

The gain adjustment circuit 61 in the detection signal processingsection 32 shown in FIG. 15 performs a gain adjustment process in orderto correct the output signal of the optical sensor 17 against avariation of the wavelength sensitivity of the optical sensor 17. TheA/D conversion circuit 62 converts the signal from the gain adjustmentcircuit 61 into digital data. Consequently, data corresponding to thelevels of 240 to 255 of the test signal are stored as illuminationprofile data of the pixel element into the memory 63 of the correctioncircuit section 33.

For example, where the GLV device 23R includes 1,080 pixel elements, themeasurement procedure described above is repetitively performed by 1,080times to perform a measurement for the 1,080 pixel elements of the GLVdevice 23R in a similar manner. Then, resulting illumination profiledata are stored into the memory 63.

It is to be noted that the other pixel elements other than the measuredpixel element are masked from the light.

Step S64:

After the measurement is completed for all of the pixels of, forexample, the GLV device 23R, the laser light source 21R is extinguished.

Step S65:

A similar process is successively performed for the laser light sources21G and 21B to perform a measurement for all of the pixel elements ofthe GLV devices 23G and 23B.

Also measured illumination profile data of the pixel elements of the GLVdevices 23G and 23B are stored into the memory 63.

The illumination profile data of all of the pixel elements of the GLVdevices 23R, 23G and 23B are represented collectively as functionsIQr(v, x), IQg(v, x) and IQb(v, x), respectively. Here, the variable vrepresents the driving voltage, and the variable x represents theposition of each pixel element and is used for identification of thepixel element. Reference characters r, g and b represent the primarycolors of red, green and blue, respectively.

Step S66:

After the measurement for all of the pixel elements of the GLV devices23R, 23G and 23B using the laser light sources 21R, 21G and 21B isperformed, the measurement of an illumination profile is ended.

The illumination profile data of all of the pixel elements of the GLVdevices 23R, 23G and 23B stored in the memory 63 are analyzed by thecorrection value calculator 64 b of the correction circuit section 33.

FIG. 34 shows a configuration of the correction value calculator 64 b.

Referring to FIG. 34, the correction value calculator 64 b includes avoltage/luminance conversion section (L/V) 281, a memory 282, an idealmodulation characteristic function production section (IVO) 283,multipliers 284 a, 284 b, 284 c and 284 d, a luminance distributionanalysis section (LDA) 287, correction table production sections (CTG)285 a, 285 b and 285 c, and data table storage sections (LUT_R, LUT_G,LUT_B) 286 a, 286 b and 286 c. The memory 282 stores modulationcharacteristic data of the pixel elements. The ideal modulationcharacteristic function production section 283 produces a desiredmodulation characteristic function.

Now, operation of the correction value calculator 64 b is described withreference to a flow chart of FIG. 35.

Step S71:

Illumination profile data IQr(v, x), IQg(v, x) and IQb(v, x) of all ofthe pixels of the GLV devices 23R, 23G and 23B are measured with respectto the R, G and B laser light sources and stored into the memory 63.Then, the correction circuit section 33 processes the measurement datato correct them.

Step S72:

The voltage/luminance conversion section 281 analyzes the illuminationprofile data IQr(v, x), IQg(v, x) and IQb(v, x) to extract a maximumvalue of the illumination profile data with regard to each of the pixelelements and set the maximum value as a value of the illuminationprofile of the pixel element to lead out illumination profiles IPr(x),IPg(x) and IPb(x) of the light sources 21R, 21G and 21B.

Further, the voltage/luminance conversion section 281 converts thevoltage values IPr(x), IPg(x) and IPb(x) into luminance values Pr(x),Pg(x) and Pb(x), respectively. A method similar to that used in thesecond embodiment can be applied for the particular conversion methodhere.

FIG. 36 illustrates an example of the measured illumination profilesPr(x), Pg(x) and Pb(x).

As seen in FIG. 36, each of the illumination profiles of the lightsources 21R, 21G and 21B exhibits a great variation.

Step S73:

The modulation characteristic data Isr(v, x), Isg(v, x), Isb(v, x) ofall of the pixel elements of the GLV devices 23R, 23G and 23B are readout from the memory 282.

Step S74:

The multipliers 284 a, 284 b and 284 c multiply the illuminationprofiles Pr(x), Pg(x) and Pb(x) and the modulation characteristic dataIsr(v, x), Isg(v, x), Isb(v, x) of the pixel elements to calculatemodulation characteristics IYr(v, x), IYg(v, x), IYb(v, x) eachincluding an illumination light distribution.

FIG. 37 illustrates modulation characteristics IYr(v1, x), IYg(v1, x),IYb(v1, x) each including an illumination light distribution andcalculated when the level v of the test signal is v=v1.

Step S75:

The luminance distribution analysis section 287 analyzes the luminancecharacteristics IYr, IYg, IYb, for example, illustrated in FIG. 37,divides them into several portions in the direction of the pixelarrangement and determines a maximum luminance function IYmax(v, x) ofthe white which can be realized for each divisional portion.

The division may not be uniform division, and, for example, as shown inFIG. 38, the pixel region is divided into three portions. Then, a commonminimum value IY0 is determined for each of the divisional regions todetermine a maximum luminance function IYmax(v, x) of the white whichcan be realized as given below:region 1: IYmax(v, x)=ax+b,region 2: IYmax(v, x)=c, andregion 3: IYmax(v, x)=f−dxwhere x indicates the position of the pixel.

The luminance distribution analysis section 287 outputs the maximumluminances IYmax of the white which can be realized, and the idealmodulation characteristic function production section 283 outputs anideal modulation characteristic function IV(t) designated by the user.The multiplier 284 d multiplies the function IYmax and the functionIV(t) and sets results of the multiplication as target modulationcharacteristics IT (v).

Step S76:

The correction table production sections 285 a, 285 b and 285 c correctthe driving signals for the individual R, G and B illuminations and forthe individual pixel elements based on the calculated target modulationcharacteristics IT(v) and the modulation characteristics (see FIG. 37)IYr(v, x), IYg(v, x), IYb(v, x) for the individual pixels obtainedactually by the measurement so that the ununiformity in luminance andcolor displayed may be eliminated. The correction table productionsections 285 a, 285 b and 285 c thus produce individual correctiontables for the driving signals.

A similar method to that described hereinabove with reference to FIG. 24in connection with the second embodiment may be used as the particularcorrection method in this instance.

In particular, the driving voltages to be applied to the pixel elementsare corrected so that the pixel elements may display with an equalluminance value Y with respect to a predetermined initial drivingvoltage Vin.

The corrected driving voltages for all of the pixel elements of the GLVdevices 23R, 23G and 23B obtained in this manner are written into thedata table storage sections 286 a, 286 b and 286 c, respectively,thereby completing the correction process.

When an image signal is inputted later, the driving signal is correctedsuitably for each pixel element and for each driving signal level by thedata table storage sections 286 a, 286 b and 286 c to correct theununiformity in luminance and color, and consequently, a video image ofa high quality is outputted.

FIG. 39 illustrates luminance profiles after the ununiformity inluminance and color is corrected.

As seen in FIG. 39, when the corrected driving voltages are applied, theluminance profiles IYr, IYg and IYb of the laser light sources 21R, 21Gand 21B are equal to each other, and therefore, the white can bedisplayed correctly.

According to the present embodiment, since the GLV devices are drivenwith corrected driving signals wherein the ununiformity in illuminationcondition and the dispersion in pixel element characteristic arecorrected for each pixel, a video image of a high quality free from theununiformity in luminance and color can be provided on a screen.

Further, since the illumination ununiformity which is liable to beinfluenced by an environment or secular change can be correctedsuitably, a video image which is normally free from the colorununiformity can be provided.

Furthermore, since a maximum luminance function is set for each of aplurality of divisional illumination regions, the luminance can beutilized effectively without being wasted. Further, since the luminanceratio of R, G and B is fixed in each divisional illumination region, thecolor ununiformity which deteriorates the picture quality does notoccur.

Further, since only an illumination profile is measured immediatelybefore an image is displayed, the measurement time can be reducedsignificantly. Therefore, the waiting time of the user can be reduced.

Fourth Embodiment

An image display apparatus according to a fourth embodiment of thepresent invention has a basic configuration similar to that of thesecond embodiment described hereinabove with reference to FIGS. 12, 13and 15. However, in the present embodiment, the image display apparatusadditionally includes a processing circuit for reducing the influence ofa quantization error which appears when driving voltage correction datastored in the data table storage section are inputted to the drivingcircuits.

FIG. 40 is a block diagram showing a configuration of part of the signalprocessing section 301 in the image display apparatus according to thepresent embodiment.

Referring to FIG. 40, the signal processing section 301 shown includes avideo signal input processing section (VSIP) 302, a data table storagesection (LUT) 303, an error diffusion circuit (EDC) 304, a D/Aconversion circuit 305 and a driving circuit (DRVC) 306.

In FIG. 40, the video signal input processing section 302 processes avideo signal VIDEO in the form of RGB signals. For example, the videosignal input processing section 302 converts color difference signalsYCbCr (YPbPr) inputted from a video image reproduction apparatus such asa DVD reproduction apparatus into RGB signals and converts the RGBsignals to which a nonlinear characteristic (γ characteristic) isapplied into those of a linear characteristic through an inverse gammacorrection process. Further, the video signal input processing section302 carries out a color space conversion process for the RGB signals inorder that the RGB signals may correspond to a color reproduction rangeof the illumination light source. The video signal VIDEO processed inthis manner is inputted to the data table storage section 303.

Corrected driving voltage data of all of the pixel elements of the GLVdevices 23R, 23G and 23B are stored in the data table storage section303. When the video signal VIDEO is inputted to the data table storagesection 303, using a driving voltage corresponding to the video signalVIDEO as an initial driving voltage, the corrected driving voltage dataof all of the pixel elements of a corresponding one of the GLV devices23R, 23G and 23B are read out from the data table storage section 303.The driving voltage data are supplied through the error diffusioncircuit 304 to the D/A conversion circuit 305, by which they are D/Aconverted, whereafter they are applied to the driving circuits for thepixel elements of the GLV device.

Since the corrected driving voltages are applied, the ununiformity inluminance and color on the screen is eliminated, and an image of a highpicture quality is displayed on the screen.

The D/A conversion circuit 305 converts the digital driving signalinputted thereto into an analog signal. The driving circuit 306 appliesthe analog signal to the ribbon electrodes of a predetermined pixelelement of the GLV devices 23R, 23G and 23B. The GLV devices 23R, 23Gand 23B operate in response to the driving signal and modulate the laserlights emitted from the red laser 21R, green laser 21G and blue laser21B, respectively.

A D/A converter and a driving circuit placed on the market and used asthe D/A conversion circuit 305 and the driving circuit 306 have a bitwidth of 8 bits.

Meanwhile, as described in the description of the second and thirdembodiments above, when a correction table is determined based on atarget modulation characteristic and a modulation characteristic foreach pixel measured actually, measurement and correction processes areaccurate processes. Thus, in order to secure a measurement accuracy, acorrection accuracy, and an arithmetic operation accuracy, it isnecessary, for example, to use an interpolation process or a likeprocess to perform the processes described above using a data format ofa great bit number and produce a correction data table for a drivingvoltage with a great bit number. For example, the bit number of data ofthe corrected driving voltage is 10, that is, the bit number ofcorrected driving voltage data of all of the pixel elements stored inthe data table storage section 303 is 10.

However, if data of the data table storage section 303 are inputted tothe D/A conversion circuit 305 and the driving circuit 306, then thedata of the data table storage section 303 which are comparativelycontinuous to each other are sampled out, or in other words, quantized(digitized) into 256 values.

The quantization makes the gradation of the driving voltage rougher andgives rise to an error when compared with the corrected data of thedriving voltage stored in the data table storage section 303. The erroris represented as quantization error.

If some discontinuity between pixels appears on the screen due to such aquantization error, then this cannot be eliminated even if thecorrection methods of the second and third embodiments are used.Besides, since the sensitivity of the eyes of the human being is high,such a small discontinuity between pixels as mentioned above isrecognized as an unnatural display by the human being. Particularly in adisplay apparatus wherein modulated lights from GLV devices are scannedto display a two-dimensional image, since a one-dimensional image isscanned on the screen, an abnormal point on the one-dimensional imageappears as a horizontal stripe on the screen and can be recognizedfurther readily by the human being.

Therefore, in the present embodiment, the error diffusion circuit 304 isinterposed between the data table storage section 303 and the D/Aconversion circuit 305 and driving circuit 306 to allocate aquantization error appearing at one pixel on the screen to a pluralityof pixels around the pixel and further allocate the quantization errorto a plurality of pixels in a predetermined region of a next frame.Further, also with regard to all pixels in one screen, a quantizationerror of a pixel of an object of processing is diffused to a pluralityof pixels in a predetermined region of a current frame and a next frame.As a result, errors over an overall video image are minimized to makethe displayed image more natural.

Although a method of diffusing a quantization error in a singlestationary screen, called two-dimensional quantization error diffusionmethod, is known, the image display apparatus according to the presentembodiment is an apparatus for displaying a video image and a pluralityof frames displayed successively have contents of the screen also whichare almost continuous to each other. Therefore, in the presentembodiment, in order to reduce the discontinuity on the screen caused byquantization errors of the driving voltage to the utmost, a quantizationerror diffusion process is performed also between frames (suchquantization error diffusion process is hereinafter referred to asthree-dimensional error diffusion).

FIG. 41 is a block diagram showing an example of a configuration of theerror diffusion circuit 304 in the image display apparatus according tothe present embodiment.

The error diffusion circuit 304 includes an adder 311, another adder312, an error rounding processing section (ERP) 313, a subtractor 314,and an error filter (EFLT) 315.

The data table storage section 303 divides driving voltage correctiondata of 10 bits stored therein into high order 8 bits and low order 2bits and outputs the driving voltage correction data as such.

The high order 8 bits A(x, y) are inputted to the adder 311 while thelow order 2 bits B(x, y) are inputted to the adder 312 and processed asan error.

More particularly, the adder 312 adds the low order 2 bits B and anerror E(x′, y′) of 2 bits appearing with a pixel in an immediatelypreceding line or in a predetermined region (x′, y′) in an immediatelypreceding frame. A result G(x, y) of the 2-bit addition is processed bythe error rounding processing section (ERP) 313.

The error rounding processing section 313 has a predetermined thresholdvalue UO set therein and receives data of 2 bits as an input thereto.The error rounding processing section 313 compares the inputted datawith the threshold value UO and outputs, for example, 1 when theinputted data is equal to or higher than the threshold value UO (thatis, D(x, y)=1 in FIG. 41), but outputs 0 when the inputted data is lowerthan the threshold value UO (that is, D(x, y)=0 in FIG. 41). Forexample, if 1 is outputted when the inputted data is equal to or higherthan the threshold value UO, then the data is referred to as first data,but if 0 is outputted when the inputted data is lower than the thresholdvalue UO, the data is referred to as second data.

The adder 311 adds the data D(x, y) outputted from the error roundingprocessing section 313 to the low order 2 bits of the high order 8 bitsA(x, y) and outputs resulting data as corrected driving voltage dataC(x, y).

The error filter 315 sets a difference E′ between the input data G(x, y)and the output data D(x, y) of the error rounding processing section 313as a newly appearing quantization error E(x, y) and allocates thequantization error E(x, y) to surrounding pixels with weightingcoefficients corresponding to the surrounding pixels applied thereto.

The error diffusion circuit 304 operates in the following manner todiffuse a quantization error.

The high order 8 bits A(x, y) and the low order 2 bits B(x, h) outputtedfrom the data table storage section 303 are inputted to the adders 311and 312, respectively. The low order 2 bits B(x, y) are added by theadder 312 to an error component E(x′, y′) preceding by one line or byone frame determined by the error filter 315, and a value G(x, y) isobtained by the addition. The value G(x, y) is inputted to the errorrounding processing section 313, by which it is compared with thethreshold value UO. The error rounding processing section 313 outputs avalue D(x, y) as a result of the comparison.

The value D(x, y) is added to the high order 8 bits A(x, y) by the adder311, and a quantization error then is inputted as processed drivingvoltage data to the driving circuit D/A conversion circuit 305.

The subtractor 314 subtracts the input data G(x, y) from the output dataD(x, y) of the error rounding processing section 313 and sets thedifference as an error E′ newly occurring with the pixel (x, y) Theerror filter 315 multiplies the newly occurring error E′ by weightingvalues corresponding to individual surrounding pixels to allocate thenewly occurring error E′ to the surrounding pixels such as, for example,predetermined pixels in a next line or a next frame.

The error diffusion circuit 304 serves as a driving signal supplyingsection or a second driving signal supplying section.

The data table storage section 303 serves as a first driving signalsupplying section.

FIG. 42 is a view illustrating an example of two-dimensional errordiffusion in the image display apparatus according to the presentembodiment.

Referring to FIG. 42, for example, at a pixel (x+1, y+1), the low order2 bits B(x, y) which become an error of a driving voltage are 1. Thequantization error is diffused in an X direction (pixel elementarrangement direction of the GLV device) and a Y direction (scanningdirection) by the error diffusion circuit 304. Thus, errors of 0.1 and0.5 are distributed to another pixel (x+1, y+1) and a further pixel (x,y+2), respectively. Here, it is assumed that the error E(x, y) in thepreceding cycle is zero for the convenience of description.

The foregoing is two-dimensional quantization error diffusion.

FIG. 43 is a view illustrating a structure of an image in the imagedisplay apparatus according to the present embodiment.

As seen in FIG. 43, the image display apparatus according to the presentembodiment displays a video image. Since a plurality of frames displayedsuccessively have screen contents substantially continuous to eachother, some discontinuity on the screen arising from an quantizationerror of a driving voltage is likely to be recognized.

Therefore, in the present embodiment, in order to reduce the displaydiscontinuity between frames, an error diffusion process includinginterframe quantization error diffusion, that is, three-dimensionalerror diffusion, is performed.

FIG. 44 is a view illustrating an example of three-dimensional errordiffusion in the image display apparatus according to the presentembodiment.

As seen in FIG. 44, it is possible to apply a three-dimensional errorfilter 315 which diffuses an error not only in the XY directions butalso in a frame direction.

As seen in FIG. 44, for example, at a pixel (x+1, y+1, t) in a frame N,the value of the low order 2 bits B(x, y) which make an error of adriving voltage is 1. The quantization error is diffused in the Xdirection (pixel element arrangement direction of the GLV device), Ydirection (scanning direction) and t direction (frame direction) by thesignal processing section 301. Thus, 0.2 is distributed to another pixel(x, y+2, t) in the same frame N; 0.1 is distributed to a further pixel(x, y, t+1) in a next frame N+1; 0.2 is distributed to a still furtherpixel (x, y+1, t+1) in the next frame N+1; 0.1 is distributed to a yetfurther pixel (x+1, y+1, t+1) in the next frame N+1; and 0.1 isdistributed to a yet further pixel (x, y+1, t+1) in the next frame.

Similarly, it is assumed here that the error E(x, y) in the precedingcycle is zero for the convenience of description.

According to the present embodiment, since a circuit which diffuses aquantization error is additionally provided, a quantization errorcomponent can be reflected uniformly on a correction signal for adriving signal. Consequently, also where a low bit driving circuit isused, correction against stripe-like unevenness similar to that by ahigh bit driving circuit can be achieved.

Fifth Embodiment

A basic configuration of an image production apparatus according to afifth embodiment is shown in FIG. 45. The image production apparatusincludes several common components to those of the image displayapparatus described hereinabove, and overlapping description of them isomitted herein to avoid redundancy. The optical modulation device in thepresent embodiment may be formed from a GLV device or a DMD (DigitalMirror Device).

FIG. 45 is a block diagram schematically showing the image productionapparatus according to an application of the present invention.

Referring to FIG. 45, the image production apparatus shown includes aninitial driving signal production circuit 350, a driving circuit 351, acorrection section 352, and an optical modulation device 353.

The initial driving signal production circuit 350 produces an initialdriving signal for driving the optical modulation device 353 from aninput signal inputted thereto.

The driving circuit 351 drives the optical modulation device 353 inresponse to an input signal thereto.

The correction section 352 determines a target light intensity ofmodulated light to be emitted from the optical modulation device 353 inresponse to the initial driving signal. Further, the correction section352 determines a value of the driving signal for the optical modulationdevice 353 corresponding to the target light intensity from an intensityof modulated light emitted from the optical modulation device 353 inaccordance with the driving signal. Further, the correction section 352inputs the determined driving signal to the driving circuit 351.

The optical modulation device 353 modulates light inputted thereto andemits the modulated light.

The image production apparatus implemented with the configurationdescribed above may be applied to a projector, a display unit, aprinter, a CTP (Computer To Plate) apparatus and so forth.

Now, operation of the image production apparatus according to thepresent embodiment is described. Operation of the image productionapparatus according to the present embodiment substantially correspondsto that of the image display apparatus according to the variousembodiments described hereinabove.

First, light emitted from a light source 354 illuminates the opticalmodulation device 353. Further, the driving circuit 351 applies avoltage successively changing from a predetermined minimum voltage to apredetermined maximum voltage to all of such optical modulation devices353. An optical detection apparatus individually detects the amount ofmodulated light emitted from each of the optical modulation devices.

Then, the correction section 352 performs an initial process includinggain adjustment, A/D conversion and so forth for the signal of themodulated light measured by the light detection apparatus. Further, thecorrection section 352 uses the amounts of modulated light measured bythe light detection apparatus to analyze and detect the ununiformity inluminance and color of an image produced from the image pixel elementsof the optical modulation devices to determine an optimum drivingvoltage to be applied to each pixel element of each color with respectto a predetermined initial driving voltage. The correction section 352produces a data table of the thus determined optimized driving voltagedata and stores the data table into a memory of the productionapparatus.

When an image is to be displayed actually, the stored driving voltagedata table is used to apply suitable driving voltages to the individualpixel elements of the optical modulation device.

When the driving voltages optimized in such a manner as described aboveare applied to the optical modulation devices, the optical modulationdevices modulate light emitted from the light source to produce animage. At this time, for example, the modulated light is scanned bymeans of a scanning section similarly as in the embodiments describedhereinabove to produce an image. The light source may include aplurality of different single-color lights. Or, if necessary, a colorfilter, a projection lens or a condenser lens may be used incombination.

With the image production apparatus described above, the ununiformity inluminance and color of an image to be produced can be reduced.

While the present invention is described in connection with preferredembodiments thereof, the present invention is not limited to theembodiments described above but allows various modifications withoutdeparting from the spirit and the scope of the present invention.

While, in the embodiments described above, an example of configurationsof an image production apparatus, an image display apparatus and amodulation device adjustment apparatus according to the presentinvention is described, the configurations can be modified in variousmanners.

Further, the method of dividing an illumination region described inconnection with the third embodiment can be applied also to the secondembodiment.

Further, while, in the image display apparatus according to the presentinvention described above, one pixel of a GLV device includes six ribbonelectrodes, the present invention is not limited to the specificconfiguration.

The application of the three-dimensional error diffusion methoddescribed hereinabove in connection with the fourth embodiment is notlimited to an image display apparatus which uses a GLV device.

1. An image display apparatus for successively displaying a plurality offrames in which a plurality of pixels are disposed in a matrix,comprising: a plurality of pixel elements for individually forming thepixels; a driving circuit for applying a driving signal to said pixelelements; and driving signal supply means for allocating by diffusion,when a predetermined object one of the pixels is to be displayed, aquantization error appearing, when driving signal data is inputted tosaid driving circuit, in the driving signal of an object pixels elementwhich corresponds to the object pixel to plural ones of said pixels inthe proximity of the object pixel in a current frame being displayed andplural ones of the pixels within a predetermined range in a framedisplayed next to the current frame, adding the allocated quantizationerror components to the driving signal data for the plural ones of saidpixel elements and inputting the resulting driving signal data to saiddriving circuit so that said quantization error is reflected uniformlyon a correction signal for the driving signal.